What does this do... exactly?
When you use the final word of the Dragon Aspect shout, you are granted the True Dragon Aspect lesser power. This power transforms you into a fully controllable dragon with full collision.

So, how powerful is my new dragon form?
I'd say it's pretty powerful:

• You have a 25% resistance to Fire, Frost, and Shock.
• You are immune to Paralysis.
• Your base health is multiplied by 5.
• You have access to every shout you've unlocked so far, except Dragon Aspect. 
• Your shouts recover 60% faster.
• You can use two different melee attacks that dragons can usually perform: the bite and the tail slam. 
• You fall slowly and are immune to fall damage.
• You can fly, and shout while flying.
  

However:

• This form cannot be used indoors.
• You do not have access to melee attacks while flying.
• You cannot equip weapons or spells.
• You cannot equip armor, though you could cast a Mage Armor spell before transforming if you so wish. I'm sure that any sort of Auto-Caster, such as Ocato's Recital from Apocalypse, would also work.
• For now, Whirlwind Sprint is non-functional in dragon form. This is planned to be fixed, but this shout is unique among the others and doesn't exactly work the same way as the others.
  

Here's the real question: how do I control my dragon form?
This is the most intuitive way to play as a dragon. Here's the controls:

• Movement and rotation are your standard movement controls.
• Your Right Attack control performs a bite. This is LMB by default.
• Your Left Attack control performs a tail slam. This is RMB by default.
• Your Shout control causes you to cast your equipped shout. Whodathunkit? Pro tip: if you are having a hard time seeing what you're trying to hit, zoom your camera in as close as you can; your dragon becomes partially transparent.
• To fly: Jump. Yes, that's it. You can jump midair, and you fall quite slowly.
• While flying, your Toggle Run control switches you between Hovering mode and Cruise mode. This is Caps Lock by default. 
  

Cruise Mode:
You move extremely fast in the air and use a gliding animation while falling.
Strafing is disabled.
Use this to traverse long distances or make flyby attacks.
Hovering Mode:
You move at ground speed in the air and use a hovering animation.
Strafing is enabled.
Use this to make precision attacks or landings.

• To revert your form, a lesser power called Revert Form is provided.
  

Requirements & Installation:
This mod is made for the SSE 1.6+ (AKA the Anniversary Update - This doesn't require the Anniversary Edition, however)
If you are using an earlier version of the game and have problems with my mod, please try installing Backported Extended ESL Support.
Please use a mod manager to install all of this.

• Install SKSE64
• Install Address Library for SKSE Plugins
• Install Better Jumping SE
• Install Mid Air Shouts 
• Install Pandora Behaviour Engine Plus OR Fores New Idles in Skyrim SE and the FNIS Creature Pack found in its optional files.
• Install monster race crash fix
• Install my mod.
• Run Pandora or Generate FNIS for Users. See the corresponding mod page for instructions.
• Profit
  

Compatibility:

• This mod uses the exact same method of flight as Vampire Lords Can Fly (With Collision), but it actually is 100% compatible with no issues.
• Most likely compatible with mods that add new shouts, but some modded shouts may not work or may have unexpected effects while in dragon form. It all depends on what the shout does, exactly.
• Most likely compatible with mods that change dragon skins or add new ones, such as Diverse Dragons Collection SE.
• Possibly incompatible with some mods that change Dragon Aspect. Let me know if you have any issues with specific mods.
  

A user has reported that the third word of Dragon Aspect has no VFX when he has this mod + Unique Dragon Aspect installed. 

• Certainly incompatible with mods that change dragon animations even a little bit, including KS Dragon Overhaul 2. 
• Extremely minor incompatibility with SmoothCam that causes the dragon's head to be tilted slightly to the right. Weird bug, but it doesn't affect gameplay.
• Technically compatible with True Directional Movement, but you'll likely see some quirks of flight that aren't present without it, such as turning very slowly in the air (though that particular issue can be changed with the MCM). If you are using this mod, I recommend configuring Mid-Air Rotation Speed to your liking, and setting Directional Movement (Sheathed) to Vanilla Style.
  

Other Mods That Make My Mod Cooler:

• Thunderchild, Forceful Tongue, and Stormcrown are very cool shout overhauls. Use only one of them, they are not compatible with each other. 
• Dragonborn Ascendant SSE rebalances some vanilla shouts, should be compatible with any of the three above overhauls. Load after your chosen overhaul.
• Rotmulaag SE allows you to meditate with Paarthurnax on 27 total Words. Fully compatible with Thunderchild (with the patch), but not Forceful Tongue or Stormcrown.
• Concentrative Fire and Frost Breaths or Yet Another Concentrative Shouts Mod will give you breath attacks like a real dragon. Use only one of them. Load after your chosen overhaul.
• Open Cities Skyrim lets you fly into cities. Be advised, it also needs patches for lots of other mods you might have installed, such as city overhauls.
• Remember to put my mod below all of these mods in your load order.
  

Intentional Game Design™ That Might Surprise You:
AKA Known Issues & FAQ

• How do I pick what type of dragon I am?
  

That's the neat part! You don't! This is a planned feature, however.

• What if I want to turn into a dragon without having to unlock Dragon Aspect?
  

You know how to use the command console, right? Just add the True Dragon Aspect spell to your character. Just... don't cast regular Dragon Aspect, as it will delete the spell once it wears off.

• I am over-encumbered when I am on the ground!
  

Yes, this is how I force ground motion to be slow while maintaining fast speeds in the air. Sprint is not possible on a dragon, so this is the best I could do.

• When I leave the dragon form, I am naked!
  

Sorry. Use SkyUI to favorite all your gear. This is certainly possible to fix (and I am planning to fix this in the future), but it is notoriously annoying to do so.

• Strafing on the ground uses the wrong animation!
  

Dragons don't have a strafing animation, and I cannot disable strafing while you're on the ground. I decided to enable strafing anyway because it felt much better to be able to strafe while hovering than not.

• I already had Better Jumping SE installed, but now it doesn't work when I'm not a dragon!
  

Yep. The functions of Better Jumping SE have been co-opted to make flight work for the dragon form. Unfortunately, using Better Jumping SE just for itself AND using it for my mod is impossible. You have to choose which is more important to you.

• I can access my whole inventory and spellbook, but I can't equip anything?
  

Yes, this is how I make sure you don't crash the game, but still let you use shouts and revert your form. You can equip most shouts and your Revert Form power just fine.

• Sometimes I start flying or moving really fast when I'm walking downhill!
  

Yep. Unfortunately, the Creation Kit doesn't have a way to tell if you are falling, only if you are moving vertically and at what velocity. When walking down some hills, you have a vertical velocity less than the threshold (the threshold is negative) for putting you into flight mode. Not much I can do about this, but I've tried to tweak the threshold to be as consistent as possible.

• Sometimes I continue walking in the air for a few seconds!
  

This is the same exact problem as above, except in reverse. Sometimes it takes a second or two for you to get up to falling speed, so you won't immediately pass the vertical velocity threshold for flight mode. 

• Sometimes I randomly T-Pose or have the wrong animation for a second or two!
  

Sometimes animations aren't interrupted or end too soon, I'm not sure exactly. Skyrim being weird.

• My shouts have no sound!
  

This is caused by two things: Dragons don't have a voice line for most shouts to begin with, and Mid Air Shouts doesn't play shout voice lines mid-air anyway for whatever reason.

• Sometimes I shout in the air, and then a second shout happens when I land!
  

This is caused by a weird interaction with Mid Air Shouts and the dragon shout animation, I think. This issue happens with Mid Air Shouts normally when you have a cooldown of zero seconds, according to the author of that mod, so I'm not exactly sure how to fix this on my end. Maybe I'm wrong, though.

• My shouts don't land exactly where I'm looking!
  

That's Skyrim's Third Person mode for you. Going into First Person while a dragon will cause a CTD, iirc, so this is the best I could do. I have tried a few camera placements, and this is one is the best one I've found.

• What if I use a camera mod to go into First Person?
  

You'll be looking off to the left at all times and have half your screen obscured. Good luck trying to aim like THAT.

• I can't use Whirlwind Sprint while I'm a dragon!
  

Whirlwind Sprint uses an Animation Driven animation to move your character forward at a ridiculous speed - Dragons do not have an animation for this, and I am not an animator. If you ARE an animator, and are interested in making this happen, please contact me!

• Wow! That's a lot of bugs!
  

Listen here, you little shit. You're a flying dragon with full control and collision using a limited animation set in a game where adding new animations or altering existing animation graphs is impossible without multiple different third-party software programs, none of which have an instruction manual! Making this happen at all is a miracle. Besides, this is all Intentional Game Design™, remember?

• I found a bug that isn't listed here!
  

Well, shit. Intentional Game Design™ that surprises even me needs to be reported in the Bugs section of this mod page. Thanks, I'll see what I can do.

Future Ideas & Planned Bug Fixes:

• Add a transformation animation.
• Description of Dragon Body active effect is slightly wrong and will be fixed.
• No more naked Revert Form.
• Add Left and Right Wing attacks. I had this implemented in a beta version, but the attacks seemed to not hit enemies for some reason. I've left this disabled for now.
• Configurable dragon skins.
• Get Whirlwind Sprint working.
• ROAR!
• Followers can ride you!
• Skyrim Together compatibility?
  

Ride your friend in Skyrim Together!
Being hit with a Dragonrend shout grounds you.

• Add a skill tree of some type, perhaps.
• Dragon armor?! Dragon Saddle?!?! Probably not, I suck at 3d modelling.