I have no idea how pet gearing seems to work (real gear that is player usable, not mage gear). For example, my pet is currently 105, but I can't give him Bi'Faak's Silence (lvl 105 req 1hs). This doesn't make any sense. I used to see people talking about giving pets Conflagrant gear, but I haven't heard anything about it in quite some time. Did this get nerfed? Is it still a thing?
Apart from a brief period about 5 years ago where a patch allowed pets to equip anything, once corrected and ever since, pets can not equip no trade equipment. Attunable, yes. Attuned (previously equipped by a player) no. Pets will not equip an item that has less AC on it than an item it already has equipped in that slot. So if it had a 10000 HP helm that had no AC, it would equip a new helm you give it with 1AC and no HP. Pets will only equip a new weapon you give it, if the delay is lower than the one it currently has equipped.