Personally I've added mods on top of TSO, but they're either armors or character creation related.
You can start with one of the existing lists or download the Total Visual Overhaul and then add your own mods on top of it. Some consider it tedious but I enjoyed for the short time I played it. Ultimate Skryim is definitely nice if you enjoy survival, cold matters, eating is required, sleep to level, etc. I can't speak to Serenity as I have installed it but haven't tried it yet, but have heard it's very good.
I am playing Total Skyrim Overhaul v2 at the moment but v3 is an alpha for Requiem 4.0.1 and has a lot of armors.
After upgrading my PC I wanted to play SE for stability and found Wabbajack. There's a wabbajack modlist for Ultimate Skyrim on LE, which is how I first got into Requiem but my PC couldn't run it very well even with the ENB disabled. I would second trying out the Wabbajack modlist installer.
