Yap, shadowed UF perform really good. Best I have found so far. I was using Zorks ouf mod quite a long time which was really good too.
I´m not that deep into programming but I can modify some lua code to my fittings.
Thats what I usually do. Look for things in the code like update frequency or refresh cycle.
I´m changing that to 0.3 or 0.5 depending on the priotity of having that information and measuring it.
My goal is to keep the CPU impact as low as possible. Usually below 1ms even in combat.
Working out really good so far.
BUT! I have managed to get that performance with ~20 addons installed!
Using Blizzard stuff (like raidframes) or addons that just modify Blizzard stuff to my fittings and wherever possible just plain textures or icons to mod the UI.