SPID is your best friend when running Skyrim at War.also avoid adding more Civil War NPC mods with Skyrim at War. No Convenient Horses, no Frostfall, no iNeed (though iNeed is probably safe if you disable some of it's options), etc - and I've replaced mods like W&C with Cold Behavior to further reduce script strain.
For example I use Fertility Mode (so NPCs can have babies together creating the illusion of a living word where I'm not the only agent of change) and that eats up most of my script budget for NPC-tracking mods. You'll definitely need to cut down as much as possible on script-intensive mods that track NPCs though.
On an RTX 3080 with a 450w bios (and power slider maxed) + 3600 (no OC) and 16gb of DDR4 3200 RAM I get around 30ish fps when big battles happen with lots of script-heavy mods that track NPCs, Open Cities and Skyrim at War.
