So, this is not MH specific, but I watch my incoming voltage when using the air conditioner.
If the air conditioner start up voltage drops to 110 volts or less, I never use the water heater heating element. The voltage drop indicates the campsite feed circuit does not have sufficient capacity to supply 30 amps to all the camp sites in use at the same time.
To keep my voltage stabilizer from working too hard to maintain 115 to 120 volts with air conditioner use, I reduce the AC usage on other items.
Hot water and fridge get switched to gas during the day.
As to driving with the water heater on, I do not recommend it due to the (remote but real) possibility of fire.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW