Should I do a 110 and 12v system?

Another point worth considering, you may never take the skin off again. It's now or never for wiring. If you think you might want in the future an outlet here, a charge port there, run the wire.

As far as camping goes, I'd say our sites are 60/40% off the grid.

What you do depends on where you live in the USA and what type camping you do. Eastern USA almost all camp grounds have, electric, water, sewer, clean bathroom, Hot showers, dump station. If you live out west you will find nothing at most camp grounds. There is no 110 volts anywhere in the USA not since about 1970. Everything has been standardized 120 volts everywhere. No need to have 12 volt battery power these days all lights are LED car battery and a 12v to 120v 60w inverter will power your camper trailer lights for 3 weeks. Coleman stove or propane stove works for us on the picnic table. We have never cooked inside our camper. Our 5000 btu AC is 4 amp and refrigerator is 6 amps that will not run long on a car battery ice chest is best for food if there is on camp ground electricity. 100 degree weather is miserable to camp in if it is hotter than 85 we stay home. Cold weather camping is more fun than 100 degree camping we put 14 quilts and blankets on the bed and camp in 6 degree weather with no heat. Pull back as many blankets as you need and slide in 7 blankets on top and 7 blankets on bottom we are warm as toast in snow, ice, wind, cold. Take about 100 water bottles and refill them plus some 5 gallon jugs if no camp ground water. We bought an old people potty $2 at yard sale or $33 at Walmart it works great.  Campground electricity is free with the camp site we take advantage of that.

Only campground I know in the east with no electric is Smoky Mountain National Park, they have water at every bathroom, no showers, they have real toilets these days.  Illinois is still a 3rd world country very few camp ground in the whole state only 6 that I know of, no electric, water at bathroom, no showers, no flush toilets. KOA is not considered to be a real camp ground only a place to spend the night along the interstate highway while traveling the KOA near Flagstaff AZ is $145 per night.

Only the die hard vintage people keep that 60 year old stone age technology stuff.  We trashed ours.  If you live out west a coleman stove, ice chest, LED lights, water bottles, lots of blankets for winter, is all you need to dry camp.  1 more thing people in the East dry camp but people out west boondock.  LOL