Power balance doesn't have to be important. There are (at least) two criteria for this to be true.
1. Power does not equal spotlight - there needs to be equal spotlight time for characters regardless of relative strength.
2. Character failure isn't unfun. To unpack that, upbeats and downbeats are a natural part of storytelling since before the written word. But systems with unfun failure conditions, such as loss of character, make avoiding downbeats important, and therefore character success is important, and therefore being a significant contributor to that success on a regular basis is important. But in systems where downbeats are still fun, just other forks of the story and ways to build tension and emotion, it doesn't matter nearly as much if any particular challenge is overcome and therefore power balance isn't as important.
One of my commonly used examples for this is Marvel Heroic Roleplay. Thor and Hawkeye can have a buddy night out with twists provided by Loki, and both players can have loads of fun even though their power levels aren't remotely balanced against each other.
Frieren is interesting, because she rarely pulls out the big guns. In some ways she's more of a Gandalf, who has always had a problem reconciling in RPGs how little he does with the Fellowship and soloing a Balor (something only a few of the severly OP Tolkien Elves can do).