Yes not all are 12V. Depends when you bought the unit. Cigarette lighter it will be 12V. Two prong blade plug, 110V. 110V will only work with inverter (control would be a panel near the step well if you had a factory one).
We went to 12V for all the reasons mentioned. Once TV's went the way of LED's the power draw became so low, 12V became pretty easy.
Our DVD player in the front now feeds from an OUTPUT on the Dash radio. This dash radio has a "non lock out signal". The same thing that a car does to the rear DVD headrest players. The only signal that is "locked out" is the dash screen. Which will of course come on with the parking brake engaged. (or other methods that we don't condone
That way the kids can watch a DVD while going down the road. THe only TV's on RV's that are locked out are typically Class A's where the driver can see the TV from the front seat.