Hero Armor - How Do Upgrades Work?

I've been doing some reading on the wiki & from what I understand after obtaining one of the following items -

Stolen Sunspear Armor, Ancient Armor Remnant, Mysterious Armor Piece, Primeval Armor Remnant, Deldrimor Armor Remnant, Cloth of the Brotherhood

You can turn these into a npc associated with the campaign the hero is from to "upgrade" their armor.

Heres my question: Aside from appearances, what does upgrading the heros armor actually do? Does it double their hp, increase their armor value or what exactly? Additionally it looks like there is 2 different sets per campaign. Is one better stat wise than another? Example: Cloth of the Brotherhood vs. Deldrimor Armor.

Lastly, if I put insignias & runes on a hero's default armor & "upgrade" it, do I need to salvage those insignia & runes prior to doing so, so that I do not lose them?

Sorry if these seem like silly questions. Thanks for your time!

A hero armor upgrade is only appearance and a HoM statue for the hero you upgraded. The only difference between the 2 armors a hero can use is the appearance. You can switch between armors you have on a hero by going to the a hero armor NPC with the hero in you party. Do note that a hero can only use 2 specific upgraded armor sets, ie. the eotn heroes can only use cloth of the brotherhood and deldrimor armor.
You do not need to salvage any runes, they are still on the "new" armor.

the "Armor Upgrades" (remnants) just make your hero(s) look fancy. Besides that, in order to fill your Hall of monuments you will have to upgrade a certain ammount of hero's with such upgrades..

Upgrading is purely for looks, I kinda like it myself seeing that you pretty much use henchman most if not all of the time so at least you can make them look nice. As said before, you have to upgrade their armor to put them in HoM, but it's not too hard getting them and it's kinda fun in my opinion.

M.O.X. has already upgraded armor so you can immediately put him in HoM.

Thanks guys!

I call hero armor 'vanity armor' when I sell it, so people know it is only for looks.

There's only one ingame effect of hero armor. Putting Gwen in Deldrimor armor will make your male human enemies less effective in combat as they are distracted by the hawtness. It's like a debuff.