It is good to read each of your stories and solutions on dry camping survival. Knowing the tank capacities would be a plus. I believe our XTC is the smallest tanked RV to chime in here with 18 fresh, 14 black, and 12 grey. But that's only part of the story. We carry an additional 6, one gallon HD plastic jugs for coffee, tea, and cooking from our well. If the trip includes more than just Jeanie and I, I can carry another couple 2.5 gallon water jugs, and if push comes to shove, I have a 25 gallon plastic pickle jug. We use paper plates and wash any utensils in a plastic tub in the sink. The grey agua then waters the outdoor plants. Our biggest limitation is the black tank.
We can get around everything else, like food, power, and G. I. showers but the black has a definite end date without a dump.
Unless you are 4WD equipped like us to handle being really way out there, there is usually some kind of water dispensary around. You've had much good advice with the above posters, so I can only add: just get out dry camping and make your own mistakes. We did a 9K mi. trip to AK in 2003 and started out with what we thought we would need to dry camp most of the time. We wound up using campgrounds more than we thought because many had a laundry room and we only took 10 days worth of clothes on our 32 day trip. It was also nice to plug into the cable for our tiny TV to get the news and weather report.
The sad fact is the party is over after 5 days. So much of this has to do with traveling style. We dry camp, boondock, use NF, Fisheries, Wildlife, COE camps, State, County, City campgrounds, some of which are very good, and also enjoy the challenge of Layovering in big cities. It's a cousin to stealth camping, because there is no camping involved: just a layover. It's a whole different topic. But, our TC is not very big and does not change shape. Recently, I've been using a right size aluminum step ladder instead of the scissor steps, which I hang on the rear ladder when we're in for the night. With the shades drawn, and nothing outside the camper, it looks like no one is home.
We move almost every day while on the road. We're into the traveling part, not the camping in one place part. All LED lighting. We carry a Honda 2k genset for an off time we may stay more than 2 days, as the 3 group 31 batteries will drop to 12.2v. in about 3-4 days if using the furnace in the morning. Our whole rig is 20 feet long, 10' 3" tall, and weighs 10,400 pounds loaded. 7200 pounds are truck.
On the way up the jeep road to crest and camp near 13, 600 foot Imogene Pass in the San Juans:

regards, jefe