I've been playing the game with nothing else opened, except task manager in the background to check what was going on.
Apparently sometimes (specially when in wrong turns, accessing menus, or combat, and some other random times) it eats CPU and GPU like crazy, then goes back to normal. Something I've noticed is that in the task manager there are 3 game process... Game.exe (32 bits), Game.exe (32 bits), and Game.exe (32 bits) (2)... By the way, I use windows 10 64 bit. It seems that the one with the (2) is the main process, but still I found it odd. Also in theory my Java is up to date.
EDIT: Something I've noticed is that after you startup the game, it runs well for about 3-5 minutes, then starts to slowdown or freeze. Hope all of this info helps.
About the engine, yeah, I've heard of similar problems with the RPGMaker MV engine, so it could be something about it and not the game itself. I'll look further into it, thanks a lot for your response, oates. Despite the freezes and stuff, I'm loving the game. So again, ty.