Disney does not put holds on credit cards or debit cards - i've used both, and i check my accounts religiously when traveling so that I can report fraudulent charges immediately. They don't put a hold on anything.
The amounts you're referencing are for spending limits on the card before it needs to be charged by the resort:
$500 at Value resorts
$1000 at Moderate resorts
$1500 at deluxe resorts
This means, you can charge up to that amount during the course of your stay. Once your account hits that amount, Disney will charge your card, and you have a new $500/$1000/$1500 limit before they charge you again or you check out, whichever comes first. The cards i use at Disney are for an incidental bank account that has a relatively low balance usually (used for emergency travel funds mostly) or a credit card with a $1000 limit (don't want any would-be scammers to be able to get more than that off of my cards). Never, ever, ever in 15 visits as an adult on my own with my own cards have they pre-charged a card on my account to check the limit, or set a hold for the funds. Never. When we stayed at the Poly, i know i used my debit card as it was the only card number i could remember off the top of my head when i did online check in. Had they tried to hold $1500, they wouldn't have been able to, i didn't have more than $600-$700 in the account that time.
They did, once, charge the card i had put down on the room for the balance of my room-only reservation. Which I discussed with the manager at the resort - it was fine, but that wasn't how i was intending to pay the balance, so naturally i was concerned with this practice, and I was assured that this is not supposed to happen. So do be vigilant about that. I have gone back 3 times since that happened, on room only reservations, and never had that happen again, so it probably was an accident, but keep an eye out on that.