Does ED-E need to be upgraded in order to perform better..? Or...do the upgrades only provide perks for the player and companions..? Can ED-E ever be permanenty destroyed..? Thanks, gang...!

Permanently destroyed only on hardcoe mode I think. I believe you can upgrade his weapons or armour at the Followers of Apocalypse or BoS

ED-E can receive one upgrade from either the BoS or the Followers. These directly improve either his DT or DAM.

All companions can be permanently destroyed on hardcoe mode, but are marked as 'essential' while companions of the player otherwise.

ED-E can receive five additional upgrades with the Lonesome Road DLC, but these are perks applying to both ED-E & The Courier.

-Nukeknockout

Ed-E is boss. Regardless of the upgrade you choose. Though I believe that armor upgrade would be the most ideal of them all.

The Laser is the most ideal if you are not on hardcoe.