Lots of cool side quests, a main quest that is one of the best from Bethesda, exploring the universe. And yes even the power puzzles from time to time to unlock a new power. I have about 100h (hard to say as steam is not logging the time for me anymore because I use mod manager and sfse) now (started with modding after entering NG+ at about 40h and still find new fun things to do. I am in NG+2 at the moment.
Mods I use are mostly cosmetic (I love to change some posters or magazine covers when ich switch NG+) or QoL like faster animations or better UI.