No speed issues with WINE; it’s not an emulator, just a (partial) replacement for OS functions. The problems are always about compatibility. It runs demanding games like Witcher 3 just fine, as well as Windows builds of most Unity/Unreal/Godot games.
I find it convenient to develop in Linux and test mostly in WINE - however, it’s more forgiving than real Windows so it is necessary to test on Windows occasionally.