Looking at the existing games I would expect to see pretty big performance and graphical jumps in Zelda. BOTW and TOTK have issues with frame rate and pop-in and general textures.
MK9 or 3D Mario I would question where they can really go graphically and what maybe a more powerful machine could offer from a gameplay perspective instead.
Metroid should be their real "pushing the hardware to the limit" showcase but I don't know.
Pokemon will probably still run terribly but will sell millions. LOL.
I think the Series S claims some are making are absolutely wild, and I seriously doubt it's going to come anywhere close to that.
Series S has its own problems, but it is still a fairly powerful machine. I have one and it's pretty gay tbh, but that's because most devs (especially Microsoft) seem to focus on adding current-gen graphical features at the expense of resolution, so most stuff looks blurry af on it, and a lot of games suffer from horrendous pop-in. Being more selective and sensible would have most stuff running nicely at 1080p or 1440p. We're talking 3.5 TFLOPS though, which a docked Switch 2 is not even going to come close to, let's be serious.
It'll be close enough to base PS4, but the modern architecture and features will also complement that somewhat.
So, I expect all first party Nintendo games will look just lovely, and Nintendo will be sensible when it comes to mixing muh graphical showcase with framerate and art style - likely favouring the latter two heavily while still, unfortunately, not implementing good AA, unless DLSS can somehow save the day a little.
It will be up largely be up to 3rd party devs how they approach the machine, but I think those that opt for graphical showcases are going to be another in a long list of cases of french frying before they pizza. They're going to have a bad time. So yeah, they might get Cyberpunk running, for example, but expect dips to 360p / 480p in handheld if they decide to push graphics over practicality.
Overall, it should be a good step up from the 2017 Switch, and Nintendo games are going to look and run like liquid gold (except Pokemon).