For CRT you will be charged the full amount of the meal for your entire party, unless you currently have a WDW resort reservation with a dining plan added. If you have a dining plan, you will give a credit card number to hold the reservation, but you won't be charged anything unless you don't cancel and don't show up. Cancellations must be more than 24 hours from the reservation.
Akershus is just a credit card hold for all reservations. You won't be charged unless you don't show up, then there will be a per person no-show fee. The cancellation deadline for Akershus may be 48 hours. I'm not sure what the actual per person fees are; they differ for each restaurant that has a no-show fee.
Prepayment is also required for the dinner shows - Hoop de Doo, Spirit of Aloha and Mickey's Backyard Barbecue. A credit card hold with no-show fee is required for California Grill, Victoria & Alberts and special dining packages like the Fantasmic package or the Candlelight Processional package.