You can install another distribution on it and make the desktop the default boot option!
It’s not how I would use it but it’s a major selling point for me. I’m not stuck with the walled garden, even in the default OS!
I played both ports on Steam recently as I’m taken by a Sonic nostalgia wave. One thing that I like more in the original Adventure is that I can skip the characters I don’t like. But I have mixed feelings with the Sonic levels - there’s just too much camera and collision problems in the way. The second game fixes some of that, but the Tails and Knuckles levels are kinda boring.
Overall, I liked the games. My nostalgia was satisfied.
I have no experience with that specific game, but I connect my Steam Deck quite regularly to a 4k monitor, but running that in 1080p. Some games might depend more on the CPU and can take the bump up from 800p to 1080p just fine. I suggest you playing on the monitor you like the color/brightness the most, regardless of native resolution, locking the framerate at 30Hz and enabling FSR on the side menu. Try 1080p and if you notice a performance issue, go back to 720p.
I didn’t play the others to say it for myself. People have said exploration is more organic on the other games of the series.
I liked the gameplay but I disliked the mechanic of having to beat an arbitrary amount of bosses to unlock the next area.