When we had our inverter/charger installed, it was wired whole-house (30amp coach). Not sure how AM Solar did it, but it's just like having an Uninterupted Power Supply for the coach - when the shore power is disconnected, the inverter takes over. When the generator comes on, the inverter starts charging. Of course, we have to remember to turn off the AC and electric WH before killing external power, but even when we don't, the worst thing that happens is that the inverter overloads and shuts down. Turn off the AC and/or WH, and restart the inverter, and all is well.
If you go with AGM, DO get a combination inverter/charger if it will fit in your space - AGM and Gel cells are happiest with a staged charging using different voltages. Most older chargeres don't do that.
FWIW, we have four 6v gell cells into a 2000 watt inverter, and we can run the whole coach (minus the AC and WH) for about 10 hours on one charge - that without changing any of our normal "plugged in" behavior (Microwave, TV, computer, etc). As a matter of fact, out electrical management system even has a 20amp setting we use if we're going to be dry camping for more than a night. With that, we could even run the AC - one unit only pulls about 6 amps after it gets started - but we don't.
al