Feels like either/or, depending on how you use it. If you're parked up for a few days, I'd be a little hesitant to wire it to the starter battery. I've tried to keep it to where if everything goes to hell on the house battery, I can still start and operate the truck as normal. Maybe that's a bit...
That's mostly how I run a similar setup. The second battery (under the hood) runs "house" tasks like the fridge and most of the charging equipment, and is isolated from the "truck" battery that handles the engine and any driving accessories. Lights, the winch, etc. The third (Bluetti, but...