Anywhere in the yellow / orange / red region is viable for solar. Let's take a worst case, you only get 4.5 hours a day of solar at 80% capacity. That means an $85 / 100-watts panel at the US average of $0.145 kwh is paying for itself in a little over ~4 years.

The issue really isn't solar generation, it's power storage. I know because it's something I've been working on DIY. Deep cycle batteries are fine for emergency power or charging low-draw appliances, but are terrible at sustaining high draw loads (Peukert's law). LiFePO4 is vastly better, but it's still expensive, you're looking at $10k for a whole-home battery, which is a lot compared to shelling out $1k for a generator and a jerry can.

But I personally put a high value on silent power generation and energy independence. Knowing I own multiple vehicles that can charge off a solar panel to get around has some piece-of-mind.

I read they will do better in a cloudy environment like mine.

The difference will (only) be a few percent, and do you *need* that "easy setup" or is a somewhat more complicated construction possible?
1x 100W, $ 84.99
2x 100W, $170.99 (East-West setup?)

If you look closely, the frame on all those panels have 4 holes on the back, nice for DIY setup.

The MC4 connectors are watertight, use an extension set to get it to your charger+battery location (then cut off the connectors if the solar charger has screw terminals), and you can use MC4 splitters to connect 2 or 3 panels in parallel.

If you can spare a few extra dollars, choose an 'MPTT' solar charger, much higher efficiency (and you can connect a few panels in series, making the wiring simpler).