So far, I've only been able to use the bag (the one I found in Gizmo's room) for some semblance of inventory management. I put all my caps into it, but I can't figure out how to get them back out into my own inventory faster than one-by-one (the game doesn't give me the prompt to select how many I want to move at a time), which I'm going to have to do since I can't barter with what's in the bag without taking it out first.

The bags don't really serve any purpose. They just waste time, and they're only useful if you have trouble keeping things organized in the main inventory (which honestly shouldn't be an issue unless you're OCD). There are a couple of glitches with them where items that are supposed to be removed from your inventory don't get removed if they're in a bag, but I've never found that to be particularly consistent. Plus they usually weigh several pounds each, and they don't offer any encumbrance reduction.

I'd simply recommend getting rid of them. Just make sure they're empty first.

You need to seek out a few thousand bags and the put one cap in each. I believe this is the most efficient use of bags.

So yeah, just dump it.

About the only thing I ever used the bag for was carrying things I occasionally needed but didn't want cluttering up the inventory - rope, Rad-Away, etc. Otherwise the only real use for 'em is for the explosives trick.

I've figured out that I can open the bag in the Barter screen, but whomever I'm trading with always tells me my offer isn't good enough if any of the items I'm offering are in the bag.