Resolution might change at launch who knows. They still optimising it like every dev before launch.
If I were you I will not buy it for base XboxOne . That system not worth buying coz of its very weak hardware..
If you like Xbox then get XboxOne X or stick with PS4
I got an S for 150 last year for rare replay and use it for backwards compatibility 360 and og Xbox titles. It's my bluray player too. I'll need another few years to adapt to 4k too, my living room is just too small for a big TV.
I'm 70% a PC gamer and 30% Switch - I won't buy another console, there just not enough time for me like it is, even if the PS4 exclusive titles rock.
An upgrade to the X might be possible with a good deal. Under 300 and when I sell my S an upgrade for like 100 to 150.
Because I like the hardware and the upgrades it does towards BC titles.
Otherwise the S is fine for me.
For Red Dead 2, I'll be fine, even if it doesn't hit 900p it's still disappointing though.