I would want the inverter wire run directly to the batteries, with the biggest wire possible, I recommend using welding cable very flexible, makers it easier to route and connect
Using the generator path will make for a long run and voltage drop problems
The shure power isolator, let's the alternator charge house and engine batteries while keeping them separate, Lithium batteries can be safely discharged to a lower level than lead acid and recharged faster at more amps, so yes if you ran them down they could accept more charge than your alternator will produce, but you should only need to remove one wire to take the isolator out of the circuit to protect alternator
The relays aka solenoids provide battery combining for the EMG start button (jump start the engine from the house batteries) and battery disconnect function for RV storage,
Battle Born drop in replacement Batteries are supposedly compatible with existing RV electrical
But you do not float charge them, aka leave them on charge full time while plugged in to shore power,
