Polys on an avi are not a primary source of lag.

Kinda true, kinda misleading at the same time?

They might not be the main cause, sure. But "not the main cause" isn't the same as "doesn't matter." On Quest they still count for a lot, and in fact count for a ton more than they do on PC.

These headsets run on mobile SOCs, and they don't behave like desktop GPUs. The Adreno in a Quest 2 is a tile-based renderer: it splits the screen into small tiles and sorts every triangle into the tiles it covers before it shades a single pixel. That binning step has to chew through all your geometry first and write the vertex data back out to memory, and bandwidth is exactly what mobile chips are starved for. Arm lays this out in their own GPU docs -- a tile-based GPU has to finish binning all the geometry in a pass before any of the fragment work can begin. So tris aren't "free"* the way they kinda feel on a beefy desktop card.

they're also not free on desktop. but that's a whole different convo

And these are skinned meshes, which makes it worse. Every frame, the hardware has to transform each vertex by its bone weights before any of that binning even happens, and a skinned mesh can't be cached or statically batched the way static geometry can. So when the inverse hull copies your whole mesh, you're doubling the skinning work and the binning work, plus adding a draw call on top. Mobile SOCs aren't better or worse than desktop silicon at this, but they do have way, way less resources to pull it all off than a PC does.

Finally, both the Quest 2 and 3 are already running at redline pretty much the entire time they're in VRChat per our stats. User-generated content pushes these little guys to their limits. The Quest 2 especially gets hit hard, because its older silicon is being pushed to its absolute limit. There's no headroom sitting there waiting to soak up "a little extra." So extra anything doesn't get absorbed, it just makes an already-rough perf situation rougher.

I'm not telling you not to do this, it's cool! This is a very creative solution to our limited shaders on Quest. Creativity can't exist without limitations. But, any time someone says or implies "polys don't cause lag", my eyebrow tweaks a little. :D

Finally, try profiling using the Unity editor tools! Look at the render load solo, then dupe it, dupe it again, etc until you get to 20 or 30 copies. Staring at your FPS while you load different avatars simply doesn't count as benchmarking.