Also, I've heard that sometimes the Gunners have power armor. Is that one true?
You may well have skipped right over T-51 if you didn't load into any cells with PA in quite a bit of levels.
You should still find it on Raiders, and yes, Gunners have power armor too. Sometimes.
Forget types... where in the devil do you find RIGHT ARMS. Of all the sets and components of sets I've looted, no right arms. Ever.
The only one I got was from the fully in-tact PA from Concord.