I don't know what the diff is either, guessing high AB is more AB, kind of like double AB?
Your vessel is super, but why stick to one color of seeds? It would be fantastic to pick out several colors and maybe do spiral rope of some kind. It is very hard to pick out seeds from photos though, it would be great if you could go to a LBS and see them "in person" or "in beadyson" or whatever.
Or you could pick out a very neutral color, a beige matte, which would really make the vessel stand out.
Or shiny black, which might be your best bet, because it wouldn't fight with the other colors, and if you wore black, the necklace would fade to the background and make the vessel seem to be suspended on your chest.
Delicas are about a size 11/0, but they are more uniform, more cylindrical and have larger holes than 11/0's generally do.