I simply mounted a on/off switch in the galley of my truck camper to turn off the inverter remotely. The AIO charge controller will charge the batteries with the inverter off.I finally found the idle draw of the Growatt you’re considering: 50W.
Not 115W like someone else found, but 50W is still what I consider very high for a mobile situation.
In a camper, most items will be be the system voltage, 12V or 24V. Inverters are only needed to run the 120V items, such as microwave, TV, air conditioning or recharge a laptop if you don't have a mobile charger. The 2 biggest 120V items used in our camper is the microwave and my wife's blow dryer. (Yes, she has to wash her hair and blow dry it daily in the middle of a National Forest).
Idle draw is not a huge concern of mine, it doesn't idle because when I turn it on, I'm using it.