Is the new UI only for Series X/S or will the One/One S get them as well?

X/S is for Xbox Series S and Xbox Series X, these are the new gen consoles, a lot of new games are now being released on the newer consoles only, and that game is one of them. you will need to request a refund from your purchase history.

The Xbox one Family consist of

Xbox One

Xbox One S

Xbox One X

these consoles are technically old and becoming obsolete.

The Xbox One S is a variant of the Xbox One console. Xbox Series X/S is the newer generation of consoles. Xbox Series X/S enhanced games are only for the newest consoles not the Xbox One S. You would need to purchase the Xbox One version of the games not the X/S version of them.

Yes it will run at 30 fps on the Series X as well.

The Series X has a number of other advantages over the Series S, not just a higher resolution. The Series X has 6GB more RAM than the Series S and more capable graphics hardware. The Series X can run Xbox One games that were enhanced for the Xbox One X and
run them smoother.

Only Xbox 360 and original Xbox games that were enhanced For One X get enhanced on the Series S, but unlike that machine, they max out at 1440P. Xbox One games run as they did on the original hardware, but with their own enhancements I mentioned in my previous
reply such as smoother frame rates, unlocked resolutions and such.

For the time being, Series X and S are on par with each other frame rate wise, but only time will tell for future titles.

I'm a PC gamer (i7 and RTX 2080) as well as a console gamer. I have a Series S because I couldn't get a Series X. When the X becomes available I'll replace it.

I've not connected my Series S to my TV, it's running off my Monitor. 1080P at 120Hz is great so far.

The great thing with these consoles is their content now follows you. when I get my Series X, only old games will work and work better.

If they're Series S/X enhanced games, but are available on the One, then you can download them. There are currently only a few games that are only for the Series S/X and you wouldn't be able to ply them on the One (like Flight Simulator or The Medium).

If it's only for a Series S/X, it will not work on a One. One games will work on a Series S/X.