Is this game ungodly hard like a Castlevania type game? Or are there different difficulty levels?

Great! That makes me closer to a buying decision!

And if it helps at all, over the first hour or so of playing the monsters I've encountered in the game are much easier to hit than in castlevania, hit detection seems to be a bit forgiving and they seem to move more slowly than some monsters in games like this, but only seen a few monster types so far and only playing on medium. So I don't know if this also changes with the difficulty setting.

I play it on hard. It's way easier than La Mulana. Not the same kind of enjoyement, but I really like them both.
Edit : but in un-epic, some charecter developpement choices can give you a really hard time here and there.