The battery on a typical RV will not power major devices for long. Some lights, furnace fan are fine. TVs definitely not. You can charge a laptop/phone. You don't want to run out of batteries during the night and be without heat!
What I do:
I use the batteries for lights only.
I charge things as much as I can from the inverter in the truck while rolling. Mine is separate truck/RV.
"cheap" inverters like the one you are looking at may not work 100% on all devices. Mine won't consistently charge a macbook; the light just goes off sometimes but it will charge iphones/ipads no problem. I think the laptop charger shuts down to protect the computer when the electricity is not "clean".
