Is there a simple way to edit the deflaut equipment that hireable NPCs start with? I hate it when I give them a weapon they don't ewuip it and go around with what ever they started with.

you can add weapons to their inventory (in the inventory tab on the NPC edit window), as well as a combat style that favors the weapon you give them

for outfits, you need to edit or add a new outfit (separate record), in the inventory tab of the NPC there is a dropdown for the outfit.

What is meant by this is NPC's don't wear armor you put in their inventory, they 'wear' an Outfit, which is, as stated above, a separate record in the editor under the Character section, I believe (if not, check Misc, it could be there). You have to create a new outfit and on the NPC inventory tab, you select the new outfit you want to assign to that NPC.

Can I simply make the NPC inventory items "playable" like with the GECK?