I have a few different bands of adventurers to play different games, some high level, some low.
My current party I'm using in a short campaign is at 123XP for 4 characters so powerful; I try to make the scenarios more difficult to compensate so I have to be tactical but not so hard that I lose a PC each and every game.
I got lucky on my last game as 'reinforcements' and 'they are at our backs' cards only came out once each so I'll take that.
It's an odd game to balance but I love playing it anyway.
My advice would be to follow the scenarios in the book to start with and increase the difficulty as your party grows.
There are, I believe, two new scenario books due for 2021, there's definitely one as I did some of the playtesting, so more opportunities to get some different games in.
Some of the scenarios here suit higher powered parties, especially Demon's Gate:
http://grahamsgaming.blogspot.com/