I found the Sanctum of Secrets or whatever (Mistress of Mystery from the Silver Shroud). The entrance is pretty cool, hidden superhero base security out of the Incredibles. It was a nice touch that the Silver Shroud obsessed Ghoul from FO4 was helping the actresses' husband figure out how to make her gadgets from the radio show work IRL before the war and then after the war she basically starts training an army of heroes. His fan letters are pretty lol...basically a riff on the super fan finding continuity errors.
I found a plasma gatling gun, but it is locked behind a level 3 terminal hack. Only have level 2 ;/ But nearby was a legendary assaultron that dropped a nice chestpiece that auto-resses you if you die (50% chance) and a high level lever action rifle. Tip of people playing: Be sure to gather all the black titanium you can find. A really nice set of mid-level power armor can be made (Excavator Armor) for fairly easy mats when you unlock the quest, but each piece requires 2 black titanium scrap to make and you need the full set to make the scanner recognize you and get the quest reward.
edit: 6 black titanium per piece. But a full set increases your total carry weight budget by 100 and you get the plans for a power armor crafting station. Level 25 set, really good for the level (vs using Raider or T-45) until you get high enough to use the T-51 and T-60 sets. Easiest way, outside of mining, to get black titanium is to slaughter mole miners and scrap their mole miner scrap drops.
Also learned a trick regarding power armor. So when you find a power armor out in the world, you can't claim it if the armor pieces on it are higher level than you. You basically have to strip the frame and then you can claim the frame. However, once you own the frame, you can deploy it and then add the power armor pieces to it, then just walk away (away from other players unless you want them to jack the suit lol). After 60 seconds, the suit is recalled to your inventory with the equiped armor. You still can't wear it yet, but the frame in inventory only weighs 10 pounds, so you don't have to carry around hundred of pounds of armor you can't use. Good way to build complete armor sets before you're ready to use them.