Oh this is amazing, I wasn't even aware you could modify that file for performance. This is really cool.
I do use SKSE, but I don't currently have an ENB installed (I might later on if I end up solving my current unplayability one way or another).
I tried launching Skyrim with all the textures disabled + with lowered settings on top of that, but had the same result, which leads me to think that this is probably a RAM issue moreso than CPU or VRAM (I doubt it would be CPU, since I was in a non-crowded area outside of Solitude, maybe 5 NPCs in total). I just ordered a set of new RAM, so I guess we'll know for sure later this week. I'm tempted to say that if that isn't the issue (and if the Skyrim.ini tweaks don't work either), I probably installed something wrong? Neither LOOT nor TES5Edit report any issues, but I feel like that's the most likely culprit. Might need to revise my install order in Mod Organizer or something.