Diesel fueling when towing
Rule of thumb. Loves are the cleanest, Pilot second cleanest, but about the size of a postage stamp. Flying J normally offer rv islands, TA/Petro may require anti-biotic.
As for using truck islands, use common curtesy and understand some trucks will take longer than others, some truck drivers are professionals and some are not worth the title. Most of them are as scared of you driving around them as you are of them driving around you. If you own a GM truck good luck with the DEF nozzle reaching to the passenger side. I normally fill a jug and then take it over and fill the tank, then fill the jug and put in my tool box in case I end up needing some and can't find it at the pump.
If you have a Flying J RV rewards card you can activate the pump at any truck fuel lane at a flying j or pilot then go inside to pay. Still a pain, but normally after burning through a full tank I need to use the restroom.
As for tax on fuel. If you don't have a IFTA sicker on the side of your truck then you don't pay any less or any more when fueling at truck lanes vs. auto lanes.