I have a (2021) 2922KB which came from the factory with solar so hopefully I can share some perspectives about your wiring...
#1. The 30 Amp factory installed solar controller installed in the sink cabinet has two sets of wires. One set is from the factory solar panel. The other set goes to your battery (or batteries). The back/bottom of the solar controller is labeled (potentially very faintly) with which wires go to which connection. If you're unable to physically see the label on the solar inverter, you could always disconnect the (positive) solar cable at the solar panel connector and then use a multimeter to test the connections on your solar inverter to see which ones still have power (meaning that set goes to the battery).
(Safety notes:
If you do disconnect the positive wire to your solar panel, cover the connections temporarily with electrical tape and protect from potential grounding.
Also, in testing, never disconnect the battery connection from a solar inverter before removing the wires connecting your solar panel. Doing so will damage the solar inverter.)
#1. Continued- Yes, you have two sets of wires going from your batteries. One set should be connected to the factory installed solar charge controller; the other set will be connected to the DC side of your power converter.
To determine which battery wire set goes where:
(While not hooked up to Shore Power) You should be able to loosen your power converter and slide it out into the hall area far enough to see the battery wires coming into it (on the 12 Volt side of the converter). Have an assistant watch the wires at your battery as you move the converter 12 Volt wires to determine which set go to the converter vs. which set go to the factory solar inverter.
#2. From prior posts, I believe that your 2922 is a slider model and despite front camper differences, the rear compartment dimensions are the same as my non-slider. I had plenty of room in the left storage compartment to relocate/ upgrade all of my onboard power needs there and still have room for storage. I'm sure you likely would, too.
This past Fall I upgraded my Solar Panels, Charge Controllers, and battery bank significantly and still have space in the left compartment to carry additional items. My 2922KB came from the dealer with a single lead acid battery on the tongue; I relocated my battery to the rear left storage compartment when upgrading to Lithium Ion Phosphate.
I still need to get some wire anchors in place to clean up my wire routing, add some reinforcement to my battery rack, and finish wiring the DC-to-DC charger.....but you can see there's still plenty of storage space available despite having a 3K Watt Inverter, two Solar Charge Inverters, a DC-to-DC charger, multiple breakers/ fuse, bus bar, master shut off, battery shunt, and 4 batteries. I've attached lightweight metal shelf material I picked up at Lowe's to the studs on the front wall of the storage cabinet to use as a rack space holding most of that equipment.
