One important part for gaming is the graphics card - I cannot comment on that particular one, but I would recommend searching it like “nvidia rtx 4070 + linux” so you can find advice and recommendations. You could also hop over to www.protondb.com, select that card and see what most people are running. Or there is this linux-hardware.org page, where you find lots of info about whats being recommended.
Nvidia used to be problematic with Linux, but I also have an older Nvidia card and haven’t run into any problems (yet). Also there’s lots of new development in that area, I’m sure it’s gonna be ok. Also some distros offer preinstalled Nvidia drivers that you simply select in a driver manager - that for example is the case for Linux Mint.
Keep at it, you got this and there’s so many people and resources online to help. Best of luck!
Just for choosing: distrochooser.de - or put some distros with a tool like Ventoy on a USB stick and do a live install to test it on the actual system. The many options are a great thing, but of course not easy to get into at first. So I’d try not to overthink it, distrohopping is a hobby for some of us :D
For trying out how it looks and feels: distrosea.com
I’m using Steam without any issues on Linux Mint. If you consider that, people prefer installing the .deb from the website over flatpak or the version of the Software Manager in Mint.