I've been to Naked City Pizza/Office Bar for the Niners game this season and the Browns game in 2022. Good food, good atmosphere, cheap beer specials and plenty of Bills fans. They were never surly that I saw.
Naked City Pizza/Office Bar (off strip) or if you need to stay close to Caesar's, I had a good experience at Beer Park at Paris. It's not a Bills Backers (they are all off strip afaik) but they have good food and plenty of TV's.