Yes, its true, that many parameters can be altered by users. You can make the game harder in some areas and easier in others if you wish, I'm pretty sure the difficulty of the dungeon opponents can be altered, though I haven't tried it. And the save files are very easy to edit. I've used notebook++ with a JSON format that makes finding data easy. Some items and attributes cause effects and most of those effects are not triggered by save file editing.
The game is meant to be easy to mod.