Fridge only draws about 300-400 watts so you can run it either way.
Water heater is 1200-1500 unless you do what I did and change the heat element
(I also had to put in a new tank but while I had it on the bench I pulled the 1500 watt 120 volt element and put in a 1500 watt 240 volt element. For a resistive circuit W=IE I=E/R so W=(E^2)/R so the element I use is 375 Watts.
I have yet to trip a 30 amp breaker since the mod. Both Fridge and WH on Electric. One A/C. I do cut it off for Microwaveing