Dual booting with an existing Linux install?

I love using Fedora for general computing, but I don't like it nearly as much as SteamOS for gaming. Since my laptop is already in need of more storage, I was thinking of getting a second SSD and installing Bazzite on it. However, I've never tried to dual boot before and all the tutorials I've seen talk about dual booting with Windows, not another Linux install.

Can anyone tell me how this would work? Would I have to screw around with the boot order in the bios every time I want to switch OS, or can I have GRUB ask me which I want at startup? Ideally I'd like it to open GRUB on startup, then automatically start Fedora if there's no input for [x] seconds. And can I set it this up without nuking my current Fedora install?

Sorry if these are really obvious questions, but I didn't want to try and rely on a tutorial designed to deal with Windows. Also sorry for the lack of flair, for some reason the button to add one isn't showing for me. (Reddit's really weird for me at the moment. Recently everything *but* the draft button has been working, and now today the draft button seems to work but the flair button is gone completely. wtf?)