This one has become essential:
https://www.nexusmods.com/fallout4/mods/33947
I can't remember the last time my game has run this smooth with all these mods I have.
Other things I find essential:
Take your Cores:
https://www.nexusmods.com/fallout4/mods/14773 (This one can get a bit annoying in a different way, like if you constantly jump in and out of power armor to do crafting or something, but the number of times that I have forgotten to take out my fusion core when a sudden attack happens near the settlement leads me to believe the alternative is worse.)
Power Armor Animation Changes:
https://www.nexusmods.com/fallout4/mods/4408 (Relevant to the previous mod, this one becomes essential if you ARE one of those types who is constantly hopping in and out of your power armor, like me.)
Pack Attack:
https://www.nexusmods.com/fallout4/mods/30140 (Though I have complained about this one corrupting save files because the mod author updates it frequently, Pack Attack has just become essential to me if nothing more than as a way of the game keeping me on my toes. It is, however, A SCRIPT NIGHTMARE so lighter machines may have problems with this one)
Floating Damage:
https://www.nexusmods.com/fallout4/mods/28684 (Probably not THAT essential, unless you're like me, playing survival mode, running around with Dogmeat and another companion and one of them buggers off somewhere, gets attacked, and you can't find them. But, oh, what are those little floating bouncing numbers off thataway?)
Durable Vertibirds:
https://www.nexusmods.com/fallout4/mods/2857 (Not that essential on its own, unless you're someone who somehow always manages to end up way too close to a crashing, exploding vertibird, but with Pack Attack it becomes absolutely necessary or the Brotherhood of Steel is going to be losing vertibirds left and right.)
Darker Nights:
https://www.nexusmods.com/fallout4/mods/191 (Absolutely necessary for immersion. Also makes various other mods more essential, such as anything that modifies the Pip Boy Light, or any mod that adds vision goggles to the game. Works absolutely beautifully with True Storms.)