We used a porta potty for years, but I found I had a hard time lugging the tank to a toilet. Plus it turns out, some restrooms hsve signs prohibiting dumping of porta pottys.
We now have a Roadtrek with plumbing and an aftermarket maserator. Works much better.
However, to extend the capacity of the holding tank we also use plastic bags for #2 and dump in the trash. This saves on the extra volume of water needed to flush and we last longer without dumping. And I can "water" the flowers at home after a trip w/o any bad smells.