I don't know if there's a preference this season / version when it comes to what uber bosses can drop what mythics, but the obvious runs would be the single mat requirement ones.
More than just physical gear but that is included. From one reference (https://www.wowhead.com/diablo-4/guide/systems/armory):It's not something I use. They already had the ability to store different cosmetic builds so I'm assuming it's physical gear swap-outs?