>>319101635
basically people need to learn how to use forward pass lighting correctly (NO LIGHT MAPS at all, it's weird, but it works - learn how to use vertex lights) or, if you really want Baked GI and post processing, realize interacts with avatars which is the real problem, not your map. 

Shaders with every feature: (normals, spec, double sided, alpha, emission, some other outline, etc) will interact with the map's lightmap if it's near or full featured, and for some reason people use 4k or higher materials in every slot. You're literally trying to drive a AAA game main character level model with 4k textures (You really only need that size for the normal and albedo.) Everything else can be like 256x256 and it's just fine. Now, you're trying to do that x 30-60 dynamic, non-instanced models with read-write enabled, no streaming mip maps, fully rigged skinned meshes, all using COMPLETELY different shaders that are uncompiled for you, and not precached on your system, while doing 40 channels of audio. 
Next time your frames tank pull up task manager, and hit the performance tab: 

If your vram is capped but your gpu is doing 10%? The materials are now caching back and fourth between your ram and cpu and gpu every single frame. 
If they didn't bake occlusion properly you can't even escape it unless you go into safety mode. 

One thing I can bitch at vrchat about is that it's profiler currently only counts #of materials.
You can use 4x 8k materials on an avatar at 30,000 poly and be EXCELLENT ranked and automatically unblocked by everyone. 
Each of those 4x materials can have like 9 texture slots of 8k textures. You could make one material like 40-600 draw calls before the map's lighting hits it, and completely fill someone's ram with a single avatar and nobody will know why it's laggy. One person.
Some people do this by mistake, and if you do I don't blame you. 
Do not do this. Please. You have to render yourself too. Twice. The mirror layer is always there.