"""an appropriate low gear depends on your bike+load total weight, what sort of terrain/steepness/long climbs are realistic to encounter, and to a smaller extent imo your age, fitness etc ."""

of course its nice to have a very low gear when cycling with weight, no doubt about that. at home with any weight on the bike I use then same low gears I use with a well loaded bike, and I love the easy going. the really big roll on the back panniers of your last image looks really cool.