Looked back at my purchase history and my current one is the camplux 1.58 gpm. Looking back Ive owned ones from 1.5 to 3, during wuflu we were doing remote boat work in villages that were closed. Amazon would still ship to some of them and we would order one for the job and give it away when we left as freight out is expensive. The water pump is a par max 2. Something or other, sticker is worn off. Its current equivalent is the 2.9. Have found the lower rated pump heater heats just fine with more flow, if you change out the head to a higher flow showet handle. The bigger ones are actually hard to turn down low enough, often on the low settings it will cycle on and off so its better to over flow the smaller unit.
The par pump is from 2019 and has outlived ar least a half dozen heaters, its a bomber unit. Par makes good pumps.
As far as tanks, my current setup is a 15 gallon tank for work trips and a 3.5 gallon jug for remote travel. The 15 will do several solid showers, the 3.5 is good for one quick shower. Both jugs are from sportsmans warehouse, the 15 is a small drum and the 3.5 is a wide opening plastic water jug that appears to be a house branded ronco plastic product. Its nice for camping as alaska has remote camp sites with hand pump wells, thr 3.5 inch opening of the smaller jug is easier to hit under the well pumps than a 2 inch bung. With that said weve used all manner of tankage. On one project during the wuflu, we put weights on the end of the suction hose and then filled up a bomar fish tote with water and used it as a tank for the duration of the project.
On the shelter, thats all going to be personal preference. We've used, ice fishing huts, several Amazon pop up shelters, three 2x6's and a tarp, and on a few extremely remote sites... nothing just out traumatizing the wildlife. Current one is a sportsmams made pop up that the wife got on clearance a few years back. Its personal preference, wife has one that folds out on her camper and its much smaller than mine. She prefers it as it keeps the warm air in better, mine is substantially bigger and taller. She's normal sized, on me it looks like a parent sitting at their child's desk at a parent teacher conference.
I didn't go with a self contained unit as they had very low water flow rates and when showering off diesel soot, hydraulic oil, 400 40wt bilge water or fiberglass dust water flow matters. Seems like newer units are getting better and would probably be worth trying if you don't have high use needs.