You could go with System76, I think they have a high-end "graphics" laptop, which would be suitable for gaming. Open source company so you are guaranteed everything is compatible with Linux.
However, if money is an issue or you find something else you like, for example the Dell XPS laptops ( in the past have been very compatible with linux,) here is a tool to check the model and/or the parts (important) such as wifi, etc., to see if they are compatible for a lot of laptops.
There is no linux version. Steam/Valve has been updating their proton versions to work with BG3. I would recommend using their 'proton experimental.' If you buy from GOG, you can use Lutris, they have a runner that should install everything needed to run BG3, and it also lists some tweaks to make.