Yep. Enjoy the content that TR has to offer with characters that it supports. House Hlaalu has a lot of content (good, because in vanilla they're the most boring Great House imo), as does the Tribunal Temple. The Almas Thirr Tribunal Temple questline is, as I have stated in other Morrowind threads before, an absolute favourite of mine and the highlight of Tamriel Rebuilt so far. The Imperial guilds are all well represented - enough content to hit Level 20 simply by doing the TR+vanilla faction content for one guild and pretty much nothing else. I haven't touched anything outside of Old Ebonheart for the Imperial Legion (and that was a couple of years ago), but it now looks to have quite a bit of extra content, which is good because it was one of the most bare factions in vanilla. And finally, the Imperial Cult looks to finally have a substantial amount of content with the Firewatch rework in Embers of Empire, although it's worth noting that two of the "quests" in Old Ebonheart are just boring fetch quest garbage.I just started my first run of TR a few days ago. It's an unrivaled amount of excellent content and no one could probably see all of it in one run. You are better off having it permanently installed and interact with it as it fits your playthroughs. I'm not sure if a complete tour of all the content is even possible considering mutually exclusive quests and outcomes, etc., but even if it is, by the time you "finish" seeing everything, there's going to be 3-4 new releases. I think the best time to start experiencing TR is right now.I still don't entirely understand this concern with seeing TR or its sister projects become "complete". This isn't a product, no main quest exists that requires an endpoint, no gameplay mechanics that await untouched. It sounds, to me, similar to someone saying they are waiting for the Forgotten Realms to be finished. Everyone involved already understands that reaching the finish line is just an aspiration, they're all mostly there because they're autists who enjoy world building or modding for the sake of it.
So there you go. You've got enough content for 100% House Hlaalu, Tribunal Temple, Mages Guild, Fighters Guild and Thieves Guild playthroughs, and maybe the Imperial legion is included there? The Imperial Cult now has enough content to at least offset the weird difficulty spike that it experiences in vanilla when you start taking quests from Lalatia Varian at like Level 5.