You can play it vanilla. There is a pretty extensive graphics overhaul. It’s been a while since I’ve played but this nexus page seems to be up to date.

https://wiki.nexusmods.com/index.php/Morrowind_graphics_guide

A lot of the charm of the game is in exploring and experimenting. So, I can’t tell you much. Just know that it is not like the other elder scrolls games you’ve played and some of the systems are different.

The only thing you should know so you don’t get frustrated and quit is that the combat works on dice rolls. If you feel like you aren’t doing any damage you are probably “missing.” Work on improving your weapon skills if you want your combat to get better.

Have fun!