If you install Steam/Lutris/Bottles as a Flatpak it will use an updated Mesa stack when you run games through them. If you need a newer Linux kernel you can use the official backported version or something like Xanmod’s MAIN branch/Liquorix.
That’s pretty much it, and you may not even need those changes depending on your hardware. I recently wrote a comment on how I use Debian Stable if you want some extra opinions on how to make Debian Stable a little more livable.