people who game more than me (Switch is the only console I’ve owned since PS3):
would an XBox Series S be noticeably worse than splurging for the X/PS5, and do we think the CFB game will be fine on it?
It'll be fine.
The real answer isn't tech here. It's if you have people you want to play with online and if they favor one system over another. If you have more people on PS5 you want to online dynasty with, go with PS5. If more on XBox, go with whichever. No crossplay, afaik.