I think I previously asked but can't find the link.

Have a stripped lower along with an Aero LPK (excluding FCG) and as assembling it was hard to determine which of these parts I would upgrade.

Are LPK upgrades mostly for aesthetics?
What am I potentially missing out on by not upgrading a specific LPK?

A spring is a spring.  What do you want to "upgrade"?

Ambi and/or short throw safety
Ambi mag release
winter trigger guard
Grip that fits your hand

BCM trigger guard
V7 short throw 57 degree ultralight safety
BCM Gunfighter Mod 3 grip
BCM QD rear plate

These are my most frequent mods. I have a million A2 grips and standard trigger guards in the parts bin. The V7 safety is so expensive I only have 3. I hate ambi safeties because my trigger finger bumps the lever. If you are right handed you don't need any ambi stuff.

For everything else it's either cheap standard MIM USGI stuff or full V7 lightweight stuff.

I like to put in reduced power hammer snd trigger springs. It improves the trigger a lot and I don't have issues with failure to ignite primers.  Costs $10 from brownells