[JRTJH]

Your trailer has a "main circuit breaker" located in the power distribution panel that is rated at 30 amps. That breaker will not allow more than 30 amps to flow through the power cable and into the trailer distribution panel. It doesn't matter whether you're attached to a 30 amp campground pedestal, a 50 amp campground pedestal or a 100 amp campground pedestal, the maximum power that can pass through that circuit breaker is 30 amps. Typically, the air conditioner uses about 12 amps and the microwave about 10 amps. That's 22 amps with both running. When the A/C starts, it uses about 18 amps which would "push the use" to the maximum available in the power center. Usually there are "hidden users" of power that aren't typically considered. The refrigerator uses about 1.5 amps, the converter (supplies all 12 VDC power) uses about 5-8 amps, the water heater uses about 10 amps. Any 120VAC appliances like a hair dryer, coffee pot, toaster, small heater, etc would also add to that power consumption.

It really makes no difference which power plug you connect to at the campground pedestal as long as it's rated at/greater than 30 amps. What does make a difference is how many other campers are on that leg of power, how much they are reducing the available power (brownout) and whether you have a "true 30 amps" available on that leg of the campground distribution. Usually there are fewer trailers connected to the 50 amp system and those plugs are in better physical condition (not as worn with loose connectors in the plugs) so it often is "advantageous" to use the 50 amp power plug.

I'd question whether you should pay for (or be charged for) using the 50 amp plug with a 30 amp trailer. you can argue the point that the maximum you could possibly draw is 30 amps, no matter which plug you use, so effectively you can never "use 50 amp service" with a trailer rated at 30 amps.

That said, if you start plugging in additional extension cords, that's more than 30 amps, but that's not typically what happens......