any other huge mods that add lots of quests?
Forgotten City- 8-10 hour quest mod that takes place in one location. Very, very high quality....Easily the best thing you will do in Skyrim. The writing is top class. I can't recommend it highly enough. I rate it as the best mod I've ever played for any game!
Grey Cowl of Nocturnal - took me about 15 hours. Adds a few new locations, including an area about the size of Dragonborn that is very different to Skyrim(an Egyptian inspired desert) and features lots of really cool puzzles. Loved it.
Undeath Remastered - Cool questline that took me about 4 hours. Takes place in areas in Skyrim
Lifeless Vaults - A 3-4 hours Dark Souls inspired dungeon that has awesome atmosphere, good music and epic boss fights. Honestly, I didn't think Skyrim could 'do Dark Souls', but it can, really well. It is the prelude to a much bigger mod and is great fun.
Quaxe's Questorium - Adds by far the most content to the game. I've not done all of it, but it basically adds quests and characters that integrate pretty seamlessly in to Skyrim, including a quest chain to rebuild Winterhold and a new city called Icicle Valley, which is very good and features lots of cool quests. Just the Icicle Valley stuff took me about 10 hours(it is very, very hard too!).
Stonecrest - Adds a village near Riverwood. After a certain level they start offering you quests and you can join a new faction. I enjoyed it and thought it was integrated in to the game quite well.
M'rissi's Tails of Troubles - Adds a new interesting companion with a pretty dark and well told story. I've not done it all, but liked it and took about 6 hours. Think I'm near the end
Those are just the ones I have tried for SE.
Moonpath To Elsweyr was excellent when I played it about 4 years ago, I think it is also on SE now. Also Falskaar adds a very large new area with a storytoo, but I've never tried it.
I'd recommend all of them