I have done things to this game that morals prohibit.

Like copying a whole Skyrim main folder modded with Nexus Mod Manager from a laptop to a steam deck and "managing" this with MO2. Bonus obscenity: couldn't run the new Skyrim version instalmed on Steam Deck with the old SKSE from the laptop install, so I had to update SKSE, break compatibility with the load order, and then manualy find which of the mods to update for it to run. Do note that I have 250 mods and an historic 70+ level build on this instance.

I guess what I am saying is "you can go pretty wild with this". Start anywhere, end up anywhere, mod the shit out if it.

I would advise on following one of the "FULL OVERHAUL NOTHING UNTOUCHED" modding guide, just because why not. Most of them have some form of attention to performance that will help with your issue.

I followed lexy's : https://lexyslotd.com/

May I ask what kind of performance problem you have on what hardware ?