We had a two wheel tote... 32 gallons to empty 30 gallon tanks. Obviously, if you can lift one end, it makes a great deal of sense to have a tote just a bit larger than the tank you're emptying. Use the hitch bracket and, as stated above, keep it to a walking speed even though you're driving.
As for two wheel versus four wheel... as I understand the four wheel, the two front wheels are close together so, in theory, turning a corner or going sideways on a grade can tilt it one way or the other. With the two wheel model we had, the two wheels in the back and the single handle up front keep it stable. By the way, it's my understanding that, with the four wheel, you still have to lift it to dump.
PS: It worked great... it went when we sold the trailer. Just figured I should explain why the above is past tense.
2004 Damon Escaper LX400 4194
40' Diesel Pusher