hey put as much as you can in, but my 100ah runs my engel 90qt with a family of 4, a handful of USB-C gadgets (macbooks, nintendos, pixelbook) for 4 days no problemo, if we just burn energy and let lights stay on lots and keep restocking fridge, I usually run generator on day 3, and not for very long at all since I dont have to go all the way back to 100%.. I dont have my propane furnace in yet decided to get but I got a wave heater right now that dont use any electricity... the math from lead to lithium is not straight forward, there is so little losses putting power in and out that you get all these capacity bonuses that you didnt expect.. for example with lead, 1A for 10H is alot less consumption than 10A for 1H.. that goes away with lithium both loads are basically equal to eachother, so when your lights are on, all ur stuff is charging and your fridge is running your not just ramping up your losses like you were on lead.
just dont be surprised that you end up having like a week's worth of storage capacity, good thing is lithium prefers to be at a partial charge.. opposite again of lead that you wouldent ever want to let it dwell that long without being topped back off, since they prefer to be at full charge.
also consider is your next destination a full charge away? I'd need about 6h on the road to charge mine all the way back up if I do this system again the Westy and charge at about ~30-40A, if I had twice the battery I'd need twice the amps or it'd take twice as long.. if every 3-4 days you only drive 2-3h and your on a couple week vacation touring parks then your still going to need another charge source.. at least a good AC charger so you can top off at opportunistic locations along the way