I'm wondering what people suspect that some of the other things not shown in Legend of Korra might be like. Who is in charge of the other Triads? What do they drink, besides leechi juice? Think of it like predictions about the upcoming seasons, but for generic background things, instead of main villains or overarching themes. First, I'm going to share some of my ideas:
The Agni Kais are mostly mentioned in the context of burglaries. This leads me to believe that they are probably low-class criminals: a large gang made of many poor people. It should go without saying that they wouldn't have all of the nice things that some other gangsters have. I suspect they would be motivated by inequality & prejudice left over from the Hundred Years War. As a large, informal group, they might not have a leader, but instead make decisions democratically. If not, obviously, their leader is the strongest or most influential among them.
The Red Monsoons, I imagine, formed out of what was left of Yakone's gang. This would have made them wealthy & influential, but that might have waned since then. If not, a smart place for them to set up business would be the bay. Their crimes would probably be more political, & nuanced, due to the small area where they have a lot of water readily available.
People gotta eat something. A drink that was popular around the 1920's was something called an "egg cream," which was kind of a chocolate milk/soda hybrid. The reason it fell out of style is probably because the ingredients tend to settle in layers, so it's not practical to bottle & sell it.
I'd imagine they have soda. As for brands, I figure it would be kind of like "Fire Flakes" & "Flame-O's Noodles." Maybe something to do with sparks, or sizzling, because of the carbonation. Cans don't come into popularity until around WW2, though they might have sped this up with Metalbending. Lots of glass bottles.
I doubt tea has faded in popularity, & would not be shocked if the Jasmine Dragon is now a complete chain. Not sure whether they would modernize their decor, or try to stay traditional. Obviously, it can't be run by Iroh any more, but I imagine that the majority share of the company is in the hands of his descendants.
Apparently, Mako is a motorcycle cop. I'm guessing this was a division that was created after the Equalists were defeated, but I don't know. In general, I would imagine they realized that they were over-dependent on Metalbenders after the Equalist attack, & overhauled the system.
River rescue units were mentioned. It would make sense to give these jobs to Waterbenders, for obvious reasons. Were it me, I would not put a motor on the boat, because the Waterbenders could propel them just as fast.
Plastics must be pretty weak, expensive, or otherwise limited, since Hiroshi Sato thought that platinum was a more cost-effective solution to fighting the Metalbending Police.
I'll add other things if I think of them, or strongly agree with someone else's observations.