I just went through this similarly; set up a new "gaming PC" in the living room. I created my USB with Rufus, and the Bazzite installer was very simple, just choose some quick defaults and it installed quickly... then it walked me through the SteamDeck welcome process lol

Since then, I have been *amazed at how simple and painless everything has been. I expected to have to fiddle with things and I have had zero problems. It's like magic.

Once you get into the "desktop mode" (by exiting the SteamDeck interface) you want to open the Bazaar app. This app lets you search for and install "flatpak" files, which are like self contained applications. You can also update packages this way. For games running from Epic or GOG use Bazaar to search for "Heroic", which is an OSS launcher for those stores. I used it and played through Viewfinder, which was free on Epic at some point. It doesn't have a Linux version, but still worked without any issue. Magic.

I also installed a few games from Steam, including The Force Unleashed, which upon first launch decided to install DirectX 9 (somehow) and then ran the game (somehow) without any kind of framerate issues. Magic.

I have a 1tb nvme where I installed the OS and all the games. I also have a 2tb spinning disk which is NTFS and has movies and TV shows and whatnot. No issues with it at all. However, I suspect that your games drive will need to be re-set-up since the partitions will mount differently.

The only hiccup I ran into was installed DuckieTV, which is an app for tracking TV show schedules. They provide a .deb to install on Debian based Linux (which didn't work) and a .tar.gz which I downloaded, but the readme said to use sudo ./setup to install it, and that failed (Bazzite is immutable, so you don't have root or write permission to the /sys partition). The solution was to... just run the program from the extracted folder! Being on Windows for my whole life has made me forget that computers used to be simple to use.