The Bills defense is what's going to hurt them. They still have Josh Allen and he's pretty much Superman and can do anything, which is why you can never count the Bills out of a game, even if they're down by 2-3 touchdowns.
Chiefs are washed and with the Mahomes injury, and possible Kelce retirement, their days of being Super Bowl contenders are over. With them missing out on the Playoffs, this feels like the perfect year for the Bills to get this done, but it still won't be easy.
The two teams that worry me for Buffalo are Houston and Baltimore (if they make the Playoffs). Texans defense is just too good and they're getting hot at the right time. They beat Buffalo already once this year in Houston and if they met Buffalo in the Playoffs, they possibly might have home field (if the Texans win the division). As for Baltimore, if they win the division they would have home field and likely play the Bills in the Wildcard which I wouldn't be too crazy about. Buffalo has Baltimore's number over the last two years, but every game has been a nail biter and Baltimore would be at home. Hoping the Steelers win the division, so at least Buffalo goes into Pittsburgh for the Wild Card Round.
Not too worried at all about the Patriots or Broncos or Jaguars. Bills can likely beat those teams even on the road.
As for the Patriots, they still have a lot to prove like you said, and if the Bills met them again in the Playoffs, I always go with the QB with more big-game experience in the NFL Playoffs and that would be Josh Allen.