I started out ONLY using the side plug with a portable (suitcase) panel because our CAMP-X didn't come with rooftop. Portal panels work very well with a 30 foot pair of cables when you park in the shade and string your panel into sun. Plus, a portable panel you can angle directly at the sun so a 100watt pointed directly at the sun will often generate as much as a 150 to 180watt laying flat on your roof when the sun is low (morning, evening, or fall/spring/winter). Sounds like you are already aware, but just for others info, choose a portable panel WITHOUT a built in solar controller. The REDARC (or Victron on late models) is the solar controller.
Using the portable-only lasted about one season and I got tired of setting it up and taking it down. I ended up mounting a rooftop 200watt panel. Since then, I no longer carry the portable panel and sold it since we haven't once needed it. Most of our dispersed camping has at least some sun each day, but our 100ah lithium battery lasts for days with no solar input. By the time we need to charge, we usually drive to a new location (plenty of sun hitting solar panel when on the road) or we can charge up while driving with the DC from the truck. Of note, though, is I have a DC switch and usually keep the truck DC switched off because solar keeps us so charged up, but it's nice to have DC/DC charging from the pickup when we need it).