I think it generally just does what the in-game settings tell it to if that's what you're referring to...
If you want more details you'll have to look into DXVK (for DX10/11 games) and how Wine implements Vsync in DX9 and below games.
Vsync leads to a crash in Rome 2 Total War.
Nothing extracted yet.
As I know, Steam Proton using DirectX to Vulcan convert. But how it do v-sync? I can't find any information about Vulkan and V-Sync on linux.