You can play all the quests from both games and DLCs in TTW.
But you need to be warned that TTW is still like FNV. So if you finish the Mojave main quest, the game ends and you can't play after that.
So my advice is to do the Capital Wasteland main quest, all the DLCs and all the side quests (you want to do) of both games and then finish FNV main quest and end the game.
