My spouse and I started an entirely new seed w/ new characters for H&H. We find the progression the fun part of Valheim though, so maybe we're odd? :-)

We did re-use the same seed generation code from one of our 'old' worlds though. I haven't really noticed anything in changes in the terrain generation, but we're still in the Black Forest tier. Except for harvestable plants being much more common this time around.... We're swimming in thistle, blueberry and carrot seeds. Those are definitely more plentiful in H&H's world generation.