The C-head composting toilet that we keep in our 13' Std. has no flap valve that has to be manually set to collect either type of waste.  The solids go directly in the composting media and the fluids go directly into the holding jug.  We carry extra pelletized sawdust and an extra jug and lid.  My wife and I are in our sixties and tend to eat lightly (we are in a 13' Scamp there is not storage room for lots of groceries, we eat modest potions.)

I have made a basic wooden box that holds a small portion of diluted gray water deordorent , and  an opened handle supported plastic shopping bag for soiled tissue.  on the end of the box is a roll of tissue.  The wooden box spends most of the time under the front bench.  After we dump the jug a small amount of the "blue juice" is added to the urine jug to stop the odor.  The is nothing good about having loose poop on the road, but I prefer having to clean the toilet to having to stop everything and sponging off.

For us, the C-head was a good compromise.  BTW,   read the instructions and watch the videos.

BobH.    one of the Scamper Campers