Arm and Body Fixes for Vroid Avi's

recently been working on a vroid avatar with some hideous issues, im fairly certain some of these ill need to fix in blender but i have also been told vroid avatars usually have some issues with sdk3 vs sdk2.

When I hold my hands straight by my side the elbows pop back hard like that, I have adjusted arm length on the arm a few times and it does it no matter what though, I imagine a join or some kind of constraint issue

jacket model clips into the body, considered just making the body transparent under the jacket but its the defualt vroid hoodie, there must be a fix
lastly the hoodie pulls super hard on the texture logo, I imagine this is related to the other issues or because the logo is so close to the seam on the texture seam into the arm

Any advice or links to fixes would be awesome

You could try editing the weight painting in blender

I have noticed on my Vroid avas that when I run it through cats in blender the bones go to the wrong place and need to be reset to the right spot. Like eye bones showing up in the neck n stuff. Also if you are not carrying any of the spring bone stuff and things from the vroid armature and mesh you will need to weight paint a lot and set limits on some of your bones. prolly not a fix but these are some of the things I have noticed.

so i have brought it into blender using a VRM importer and Cats, i didn’t notice anything to strange except that the “ShoulderJoint” is pretty much in my collar bone and weighted oddly, when i tried to change it actually had no effect whatsover, the model still deforms the same way as if i hadn’t touched it. i have the body object and skeleton selected when i got into weight paint mode, im not even sure if its trying to effect the mesh im looking at or something else because things like X-Axis mirror dont seem to work either

If you are using Blender 2.91+ you have to use Vertex Groups X Symmetry instead of X-mirror.
If that doesnt help, then do Data Transfer modifier for vertex group projection or use add-ons then enable real time x-mirror projection. VRoid was never meant for FBT or VRChat and works mostly with premade animations, you need to do a lot of manual work to make it decent at least. To prevent clipping and optimize your avatar you usually delete any topology hidden under cloth, or do fixes to weight paint and topology if you still want to use outfit toggles. All of the problems you mentioned are weight paint problems, constraints has nothing to do with that.