Good ideas…
I have a regular RV pump. I have a 10 gallon RV water tank, very small, and two 5 gallon jugs with the siphon (that the word).
I want 40 gallons…, but will make do.
I have a tiny 12v pump too, probably like that $20 mentioned, and maybe it would be easiest to transfer water to the 10 gallon tank, or maybe just move the siphon hose around to the full jugs.
I imagine each trip requires different amts of water, so not always taking 40 gallons as I would boondocking many days in the where-to-find-water western states. It is a small space so not having a 40 gallon tank eat up space is a huge bonus during times I do not need that much water. I also like the option to move jugs to the truck or outside to make more space in camper.
I will be happy with 20 gallons though, and with jugs it is easier to find places to fill than trying to run a hose to an RV.
If I can find good jugs then one option is to not mount any RV tanks, but just use the portable ones as needed.
I'm still in the think out loud phase so feel free to have opinions