Honestly, to OP, you need to decide for yourself what needs to be changed or enhanced dependent on your own values/interests and the relative impact each has on performance - and I don't know whether anybody can tell you exactly what YOU need, as everyone is different and values different things.
You don't have to have any mods at all (this coming from a guy who has an absolutely crazily modded Skyrim and FE2 (actually the latter really required, imho, lol)). Sometimes less is more - and it is a great sim all by its lonesome.
Look at what is offered, as already referenced, and try various ones out - asking yourself what impact does this make for ME? -- the thing with mods with any game is you run the risk of them not getting along, adding additional "stress" (for lack of better term) to your system (and that is system unique) -- though in some cases the exact opposite, or also changing the dynamics of the game to what wasn't initially intended by the developers (sometimes this can be good, sometimes not -- it's all dependent). I would start "light" and go from there.
Indeed with the new BHaH II, I am going to try to hopefully keep mods to a minimum (looking quite forward to any and all changes the development team made to PE) :-)
But in the end, a person has to suit themselves. I am sure people will post items/mods that they themselves are quite fond of and what works well for them.
For me, my suggestion if you could only have one group of mods, I'd suggest VonS's GPU tuners (as the gain for me in both visual fidelity and fps is quite terrific!) -- and the news mod being my second (but low and behold, it is now incorporated into PE