Proper Wire Size?

The thing is many charts don't address where they "came from" or what "acceptable voltage drop" they were based on. This one here for example indicates 12 would be more acceptable, but this chart ALSO does not see to answer those questions LOL
12 Volt Wiring: Wire Gauge to Amps | Offroaders.com

The calculator on this page actually calculates based on the drop "you say" is acceptable

Wire Size Calculator

For myself, I tend to want to go WAY overboard. In fact I would likely use no12 in this case

"Somewhere" and assuming that wire claiming to be some gauge or another actually IS that size.........."somewhere" there are charts showing wire gauge vs resistance / 100 ft. If you can find that and decide what drop is acceptable, you can actually plug that in and figure it yourself.