I suggest to build 1 room with 0 upgrades. Put best 2 dwellers with good guns and E+ equipment. You will ask why?
Simple: it's very good to make quests: extinguish fire, or then you get quests about incidents, in this room fire will be extinguish in 2-4s, radraoches - always only 1 comes, if you will give guns you will kill them in 2-4s. AND your dwellers wont lose HP almost . of course my dwellers have 10+ Endurance.
I'm very happy with this room. I got new quest: extinguish fire 30 times, so i just "Rush" room, after 5s again "Rush" and etc.. it's a bit annoying because you need fire so ~90 rushes and quest finished. But it's much faster and safer and don't need to waste much more time or "skip one quest".