Posted my thoughts about Ragnarok on the dedicated thread, so I'll talk about Valhalla here.
It's almost comical how well the combat system of Ragnarok works in a roguelite setting. One of my biggest complaints about the main game was how they hardly ever forced you to use the many options at your disposal. In Valhalla, way more enemies are susceptible to specific weapons, so you have to switch between them more. But they also set you on a path to prioritize one weapon. It feels really nice to have the game choose which weapon for you to use, because I feel like they are all equally decent (unlike many weapons in say Hades 2). I'm trying out Runic attacks I never looked at in the main game for the first time, since that's all you're provided. I've only made a few runs so far, but it's a much better option for doing combat scenarios again instead of the stupid Muspelheim challenges.
One big problem I have though is PLEASE SANTA MONICA STOP WITH ALL THE FUCKING PATHS. What I loved about Hades 2 and Slay the Spire was getting into a flowstate. You're pressing buttons to access new areas or refill on resources without even consciously thinking. But in Valhalla, they return you to random hub areas that for some reason are incredibly complex for what is supposed to be a quick breather in between fights. Just put all the doors next to each other for fuck's sake, don't make me grapple four times just to check what my other option is. I mean, they went out of their way to make developing this harder, only for a worse experience (which I think is true for a lot of the main game as well).