Hello there fellow KB player
Companion/armor bearer is same thing as wife was in The Legend, he gives you some bonus and have 4 item slots. You cant have kids with him (like was case in previous game), but is still much useful for additional item slots. Different companions give different bonuses and have variable slots, so best to to pick depends of your class/army.
If you`r not sure about new companion save game before releasing one you have and taking new to check his inventory/bonuses and if you like him keep playing, if not just load.
As for items moral it only depends of it`s type and battles you take, expl : ogre club gives bonus for giant/ogre/orc chieftain so it`s moral will drop if you fight against those type of units, elven crown will lose moral when fighting any elf army, dragon slayer sword will lose moral in any fight with no dragons, and gain moral when you kill dragons, etc . . .
So item moral have nothing to do with your current companion.
Have fun playing this game