This article is for merging information and discussion, I cannot help more than this with merging issues.
Remember merging with big mods always will end up in a not optimized experience, with some features missing or producing bugs. Keep that in mind.

To merge with other modengine2 mods using the same files, you need to overwrite/merge the files from my mod I'll list below to the mod you'd like to merge with (if the mod is bigger than Elden Vins), or if it's smaller you have to get the merge info from the smaller mod to merge into Elden Vins.
This mod is not compatible with mods that also edit the vanilla gameplay, only with ones that add content or are not gameplay/animation related

regulation.bin is merged with the "Merge Params" option in smithbox

for the rest of files you'll need to unpack and repack modded files with witchybnd

chr folder:       c0000.anibnd -> a000, a001, a002, a003, a010, a014, a066 and all files between a400 to a971
c0000_aXx.anibnd are raw animation files, replace all or unpack and copy all hkx files
Remember to run ERClipGenerator to edit the c0000.behbnd file and import new tae slots added to c0000.anibnd

sfx folder: from the unpacked sfxbnd_commoneffects.ffxbnd file:
in effect folder: all files starting by f9, like f9xxxxx.fxr
in ResourceList folder: same named files as in effect folder
in model folder: all files starting by s9, like s9xxxx.flver, and s88999
in tex folder: s51065, s51005, s41271, s36020, s01108, and s01102

action/script folder: open c0000.hks and copy the added lines you can see searching for "sekiro" and paste to the final mod hks file

parts folder: mandatory files are wp_a_1060.partsbnd, wp_a_1060_l.partsbnd, and all files from wp_a_1401.partsbnd.dcx to wp_a_1514.partsbnd.dcx

For the rest or the files, they are either optional or unmergeable, or I myself don't know how can be merged.
Hope this solves some issues, but there's not much I can do. Is a difficult mod to merge because I replaced too many things related to animations that if any mod uses references to vanilla animation files it won't work as intended. My tip is just play big mods separately to have the best experience.
Or maybe using mods more easy/safe to merge, like Seamless Coop, Randomizer or Diablo Style Loot