your room charge balance is settled automatically during the night leading to your check out.
if you want to settle that charge (all or part of it) with another payment method (cash, gift card, mardi gras beads) you need to do so at front desk/concierge before your last night at the hotel, otherwise the charges will go to your CC
you can charge up to $1500 at values ad moderates, and $2000 at deluxes/DVCs. if that limit is reached, payment is processed on your CC and you get a fresh limit of the same amounts.
once you've checked out, you can no longer use the charging privileges.
you can't use the charging functions of your magic band if you're not an onsite guest.