1 - Yeah you can do this. It's slightly more complex to set up, and uses a bunch of extra hard drive space. Also sometimes Windows just decides to fuck it up. Also my experience with dual booting is that I never open the Windows partition and it ends up a year behind on security patches.
2 - You shouldn't install SteamOS. It's great that it exists though, because it's been pushing everyone towards better Linux support. Most games just plain work on Linux now.
3 - https://distrosea.com/ will let you run the installer for a bunch of distros remotely on someone else's computer. Most Linux distros just run the whole desktop in the installer, so you can experiment with that. Take five minutes to boot up Linux Mint on this and poke around; it'll make you feel kind of silly for waiting this long. Then use it to try the stuff other people recommend.
I always recommend Linux Mint (no bullshit, very well supported, Windows-like UI, easy setup, yes it runs all my games). But there are plenty of good options.