This ^^
I say having a physical card w/ number as the "main" one works best, but I always then buy the electronic delivery ones and add and move them. I actually have about 3 physical ones uploaded on the site (my main one, one my mom carries around, and a back up).
I've never hit it, but the maximum on any 1 card is $1000 though, so you may need a few "main" ones. You can also only have 6 cards on file at once, but once you've moved the money you can delete the card, so I usually leave at least 1 slot open for doing this (upload, move and delete all in the same session if needed). You can also delete other ones and they won't lose the money, you just won't have the "back up" of it online at that time. and by "back up" I don't mean that they protect it, but at least if it's on there and something happens, you have it to move the balance to a card you do have.
