At check in you will be able to add a card for incidentals / resort charges just like if you had a regular cash reservation where your final payment was due in advance.
That’s a pretty big drawback! Also generally speaking you need to be in contact with David’s a year out to get your first choice; rooms become available 11 months out and most DVC resorts sell out very, very early, especially for studios.
Most studios also have 1 queen bed and 1 pull out couch. The exceptions are: Old Key West has 2 queen beds, and Riviera, Saratoga Springs and soon, Polynesian have one Queen bed and one pull down Murphy-ish bed that has a slightly thinner mattress but is very comfortable. The pull out couches OTOH are, IMO, bad.
Also the rooms are generally smaller than their non-DVC Deluxe counterparts. Not much smaller, but smaller. Again there are exceptions. Bay Lake Tower in particular has some very small studios.