The inverter and the battery bank have to match voltage so if you are committed to an inverter that is designed for 12V DC, you cant use 24V batteries with it.
That said, 5000W is really high for a 12V system. In theory if maxing out the inverter, you will be drawing 417 Amps at 12 volts, but because inverters are often about 90% efficient, it will actually try to draw ~460A which is higher than the rating for 4/0 wire and many battery switches.
So one option is to lower the inverter to 3000W. It should be able to run a mini split and microwave at the same time. Then a 12V system is OK.
But for you, if you think you need the 5000W of peak power (you will need to research what all the big power items you would run together need at max wattage), then you should step up to a 24V system.
This drops the amperage in half for the same wattage and allows smaller wires.
The added step for a 24V (or 48V) system is that you will need a DC converter that drops 24V (or 48V) to 12V to power fans, lights, water pumps and other items that are usually 12V.
For solar panels, most current panels have similar efficiency of watts per area - so in general, a 400W panel will have twice the area as a 200W panel. For a bus, the 400W (house) panels are big (maybe 80" x 40") but there are folks on youTube with good examples of racking systems that can mount these panels effectively to a bus roof - but plan for help getting them on the roof. It is not a free-lunch situation of 400W in the same space as a smaller panel.
For solar, figure out your likely daily watt hours of energy use and see if you can replace that with solar. If you have 4 x 200W panels that is 800W and a decent rule of thumb for summer in Wisconsin is 5 "perfect" hours of sun per day = 800 x 5 = 4000 Wh. A single 24V (actually 25.6V for LFP) 100Ah battery holds ~2,560 Wh when full, so your panels could fill about 1.5 of those batteries in a day of sun (if not using other energy).
So I agree with
@nikitis that the panel wattage is low for that size battery bank.
In some ways, it does not matter if your battery bank is really big if you generally don't use much of it. If you have a 800Ah system but typically only use 200Ah of it per day, then if your solar can fill 400Ah, then you can cover your daily needs on solar and even catch back up after a few days of clouds/rain.
This stuff gets complicated because of all the overlapping layers and multiple options available. Just keep watching videos and learning.