@bazbt3 I believe 16GiB is a good size right now, so you have space to grow both the system and more apps in the near future. From what I can tell, as long as it's a Class 10 card, everything should work fine.
I'm going down your route with a USB drive for storage and everything else on some network share. Depends a little bit on what the task for the given RPi is, but in a nutshell.