Questions on S&W snubbies

[jhs1969]

I have a S&W 637 I bought for my wife a few years ago, I've since gotten her a Kahr K9 and carry the 637 during the hottest summer months myself. It is the newer version with the key lock.

I just bought a S&W 36 which I will resale to my father-in-law. It is an older version with the firing pin fixed to the hammer and no key lock and a pinned barrel.

My 637 is stamped on the barrel as .38 +P, the 36 is just stamped as .38 spcl. Would +P's be ok to use in this revolver?

Is there any advantages/disadvantages in the pinned barrel?

I'm not up to speed on S&W's older relvolvers, is there anything else I need to know?