Is there any reason for me to get an Series S ?
Because the One S / X can :
‐ still access GamePass
‐ use actual discs
It is about 100 bucks cheaper at my local marketplace.
My Monitor can output 1080p max.
The main use cases are GamePass, Sonic Games, physical copys and Youtube
If you want to use physical copies as the "main use cases" then I would suggest waiting a bit to get the Series X or getting an One X honestly or getting a Series S and later getting a Series X down the road, here's why:
Yes the Series S seems as powerful for games if not more but it doesn't have a physical drive for games, which raises the question, are you willing to give up having a physical collection, relying on the Xbox Store instead of having the physical (especially used) market as an option, and games being taken on and off as the publishers will?
If so the Xbox Series S is a great bang for your buck console, I played a few times at my friends house and it's really impressive about the amount of performance you get with your money, to be honest it just might be hard to build a PC with competing specs at the same price-point.
Overall the Series S is a great console in terms of price to performance if you're on a budget, it should last a while even maybe beyond after the market gets stable again so overall it's a pretty good investment (even if I disagree with it being digital only (IMO)).
And hey, if the Series S still bothers you on not having a disc drive you can always get a Series X down the road.