The “Ethernet” cable is routed to the area behind the wall where Airstream intends for you to install the display panel for the soar controller. You don’t have to use it for that, I used it for the controller for my multiplus inverter but others have used it for battery monitors. On my FC25 the wire terminates under the water level panel but I don’t know where it goes on yours.
I suspect controller you have is probably rated for 11amps, not watts. If that’s the case it’s not able to fully take advantage of your 300watts of solar. If both panels we’re getting full direct sun they have the potential of generating around 25 amps. Your controller would deliver less than half of that to the batteries.
A top of the line solar controller would be a Victron SmartSolar 30 amp unit such as SmartSolar MPPT 100/30 Charge Controller https://www.amazon.com/dp/B073ZJ3L13..._lKCnFbE1ZE609
. Many places stock this unit if Amazon is out. The Victron will communicate over Bluetooth to your phone so you don’t NEED a display if you’d rather not put one in.
Other units are fine just be sure it can handle at least 25 amps. Victron makes some that are bigger if you think you might add more panels in the future. MPPT is more efficient than a PWM controller.
In terms of covering the panels, I didn’t bother but it would be safer for the panels. If you accidentally shorted the wires together it might damage something. The voltage is only about 18volts so there’s no issue with getting shocked. Folks with a larger number of panels would be concerned about a lot of heat being generated in a short as well.