You have all kinds of options.
Cruising the main engine running and Generator running. Air unit on for air conditioning, outlets on for galley, head or stateroom, stove top or oven for cooking and Ice maker. You don't need to have the hot water heater on because the engine is heating the hot water heater, you don't have to have the battery charger on because the engine is charging the batteries.
Cruising, the main engine running without generator and using the inverter, outlets, Microwave are usable. You still have hot water, your batteries are being charged, your outlets are available to power 120V appliances, you can cook with the Microwave.
Anchored, and using the generator. Air unit for air conditioning is available, battery charger if you need to charge batteries, ice maker, stove top or oven, microwave, outlets, anything that is used on shore power can be used using the generator. You should use some power management. Don't have the hot water heater, air unit, stove top, ice maker, battery charger all operating at the same time. It will put the generator into overload.
Anchored and using the inverter. You have a large battery bank for the house. If you have been cruising and have the house bank fully charged you can use all the outlets and the microwave while at anchor. The hot water in the tank will last quite a while so no need to have the hot water heater on initially. All 12V accessories are available. If at anchor and you see the house bank at or below 12.3 V it is time to start the generator and charge the batteries, turn the ice maker on to make some ice and turn the hot water heater on to replenish hot water in the tank. If the generator is running get the most out of it.
Review the owners manual electrical section to understand the circuits.
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There is a rotary switch that is shore power, off, generator. To use the generator the rotary switch must be in the generator position. To use shore power or inverter the rotary switch needs to be shore power. The R31 should have the auto transfer switch which will turn the inverter on when shore power is disconnected. Make sure you understand this feature. If you do not have the Charger/inverter manual go on line down load and read the operation manual so you under stand the functions.