Enderal for a whole new world in the Skyrim engine. New map, new creatures, new spells, new items, pretty much nothing is unchanged and it's really well done.
Kingdom Come Deliverance for a more hardcore and true-life fantasy RPG
Oblivion if you haven't played it, just needs a texture mod for the most part.
It's basically better talent trees, not all that different.
For an actual different experience you need mods like Apocalypse (155 new spells) and most importantly the mod that instakills you if try to play a stealth archer.
However if you want something new, eurojank games tend to scratch same itch to me if you can tolerate unpolished game mechanics until you get used to it. Two Worlds 2 and Elex 1 is great games to start with.