There are aftermarket adaptors available for the zamp ports, so that you can use most other connector types with their "proprietary " port. (Meaning, the Zamp suitcase panels are plug and play, but an adaptor plug makes other less expensive panels just as simple to connect.)
Your friend is right. Portable solar is great. Allows us to park in the shade, and still keep the batteries charged.
I don't know which controller Oliver is installing, so yes, you should ask how many additional watts you can have in portable solar. The controller needs to be sized big enough for all the power coming from the combined rooftop and portable solar.
Edited to add: Most suitcase solar packages come with their own separate controller, which feeds directly to your batteries through Oliver's prewired Zamp port and wiring, so then you don't need to worry about the capacity of your onboard controller.
We did ours a bit differently... ( of course. 🙃)
Sherry