Is it worth putting points in this for theft? You really ever get anything good?

I don't think so. This is the first Bethesda game where I was never really that tempted to pickpocket.

Being able to put explosives in people's pockets and disarm them, or even strip them naked, is the real benefit of the perks.

Yea not sure how sneaky I plan to be though. If I were to go sneaky would rifle or auto be better?

Rifle, single shot rifles with the perk give 30% armor pen and more damage thus making the first hit likely the last

Nah. You'll find an abundance of caps and items in the wasteland

I put some points in it. I like to pickpocket fusion cores from BoS knights (what an exemplary sentinel I am!) and I'm hoping one day that I'll meet a BoS legendary with a legendary gatling laser (apparently, killing legendary friendlies makes their legendary loot disappear for some reason).

PS - robbing fusion cores from power armored NPCs forces them out of the power armor, at which point, you can steal some pretty valuable stuff.

So far I've not really found pick pocketing to be that useful, which is a shame. But to quote the Box Maaaan, it's all about the exploding pants for me.