Most (all?) of them also have a manual inflator and deflate mechanism, expect that you might have to deflate it somewhat for a btter neck fit. (If you really want to learn what a pencil neck means, try an airline life preserver. Can't fit it over your head unless you're a small woman or child, and that's without even inflating it. UGH.)
I was lucky, the Crewfit guy at a boat show I was at (that long ago) was ambushing us sailors. "Here, try this on" and then WHOOSH he hit the inflator tag. Grabbing live demos from the crowd. Well, at least I knew it fit.
By the way, when I bought my HL foulies I couldn't figure out wtf the little loops on the front by the zipper flap were for. First time I put my Crewfit on over the jacket, I found out. The PFD has little toggle buttons that button into the jacket--ensuring the correct position. And, yes, it fits around the collar. Worn bare, it rides on the back of the neck though. (New ones may be better.)
Boat show, demos! Blow it up manually if the guy doesn't want to pop a cart. The Practical Sailor review and equipped.org reviews also both say you really need to try it on in the water to get the straps adjusted properly--if you want it to float you face up. For pretty much all of them. And manual inflation is fine for that, as it also is to test once in a while to make sure there are no leaks.