What rendering optimizations does Roblox have?

I thought it does though, putting a face into the head of the character always leads to it becoming lower quality because (based on my presumption) roblox shoves the textures alongside the texutres of the clothing, cramming it down. Of course you can bypass this by making a duplicate head (basically going against the humanoid).

It just becomes lower quality usually (exponentially so if you lower your graphics level).