Why run the a/c prior to hauling it on a 12 volt system with no a/c ?
If the fridge is off, it does not need to be level.
As you are looking at the fridge , It's more important for the gas to flow evenly if the fridge is level from east to west due to the design of the tubes.
If the fridge is located on the roadside or curbside of the TT, then you use the trailers tongue jack to make it level. If the fridge should be on a rear wall or front wall, then you would level it by using the wheels and suspension on blocks.
To level it the first time. Use a bubble level inside the freezer compartment to get it level... then while its level, install levels on the outside of the trailer for easier quicker leveling.
I use a large level that i can see in my side-view mirror while pulling into a site. I just park it where its level. That eliminates using wood under the wheels most of the time.
Sometimes i find it easier to turn the fridge OFF when parking off level at a rest stop or parking lots while shopping for relatively short periods of time. It will act as a cooler for hours. Don't forget to fire it back on before you depart again.