WIndows VM: specs advice

You shouldn't set the ram to the virtual machine to as much ram as you have in your computer, you have to leave enough ram for your OS to still operate while running the virtual machine. I would recommend 8-12gb of ram for your virtual machine.

As for gaming on the virtual machine, you need to have a GPU passthrough to get good performance. virt-manager gives you powerful options to work with to set it up how you are wanting it to work. If you are using VirtualBox there are options for it there as well.

Also, if you happen to have the games you're talking about on Steam, they have a compatibility layer called Proton that you can enable in settings > steam play > check Steam Play for all other titles, and set the drop-down box from Proton experimental to Proton 6.3-8. Check ProtonDB for your games to see how well they run on Linux.