Here are my thoughts on how it would be best to build it out.

Missing from that diagram is the grounding connection (be sure to put one in), the three powerbanks (What's your plan for charging those? Just pull off the inverter? Looks like they need 18V to charge.) and any other system components that aren't mentioned in your post above (battery monitor? shore power charger?).

Additionally, the MoserMakes electrical system diagram has been a very helpful reference for me in the past, and I think it may be helpful for you. The system hub I use is linked on that page, if you'd like to use it.

As a final note, I included an inline MIDI fuse in the diagram, but you could just use an inline blade fuse since you're not running high amps--here's a cheap 10AWG that would work for you.