Frieren is a perfect example of how adaptations should be made. It takes a concept and expands on it in a way that makes sense only in anime form.
I’ve read the manga after watching the show and it was quite amazing that how every scene was there. Nothing was left out … instead the fight scenes, rare as they are were dragged from a couple of pages to 10 minutes of action with an amazing soundtrack (as OP said). It’s better in the anime, I’d say. But what do I know :D
https://www.youtube.com/watch?v=M7gm_r8hXoU
Evan Call is really good.