Yeah I don't get how to use it either. I thought it was like a credit card. So i left all my bells in the bank, thinking the money was in the card anyways. But they said I had no money. I was like ok...
Yes. I have read that you get "a box of tissues" at 100,000 bells (I should hit that tomorrow. I'll let you know. . .) and at some point you become a V.I.P, although I haven't found out the bell level or what, exactly, that means. . .
You can only carry 99,999 bells in your inventory, same as in WW. They give you the card so that if you want to buy something from GracieGrace which is, let's say 300,000 bells, you use the card to either pay it directly from the bank account or so you can come back later with more money to pay it off.