Well, from the look of things so far we have met all of the Yonkos and have a very good idea about what their characteristics are.
My speculation is that they are borrowing some themes from the Four Horsemen of the Apocalypse.
He is controlling Wano by means of the poisonous food (sorta) and his alliance with Orochi (the new Shogun), making him alike the horseman conquest/pestilence. From the look of things so far Wano had enough food to feed its inhabitants until the arrival of Kaido and his crew, people are starving and haven’t the strength to fight him off. The illness provoked by the poison in the water, the army of smile users, and all that, could be interpreted as pestilence and conquest. This horseman has many interpretations: as righteous, as pestilence, as conquest; maybe something to do with Kaido’s personality.
This one is a stretch, but she seems to borrow from famine/imperial oppression. She controls the people in her territory using fear and…sugar? Addiction to sugar, the soul payment, and her cravings basically have Totto Land under control, all sort of sugar based snacks (and its placebo effect) to feed them and the fear of being eated by big mom herself may very well be the reason why the inhabitants of Totto Land don’t bother trying to escape.
Also to be mentioned, this horseman is depicted with a pair of scales, maybe something to do with Big Mom’s devil fruits power, taking and giving life span.
Alright, this may very well be a large stretch as will be the next one. But, I believe that Blackbeard takes after the horseman Death itself. This horseman is interpreted as empire dissolution, just like he did destroying Whitebeard’s empire. Death is depicted together with Hades, and Hades goes with its jaws open receiving the victims slain by Death. Maybe this has something in common with Blackbeard taking/stealing devil fruit powers by slaying the users…
This could be too on the nose, but the horseman War riding a RED horse is the only option left. This horseman is interpreted as empire division and holding a sword upright. As Shanks does, holding his sword ready to battle in Marineford, holding his sword ready to battle Whitebeard, and also provoking division…more like discord, between the Marines when he stopped the war at Marineford, maybe/could be/should be provoking Whitebeard’s ego that just assured his no intervention in the persecution of Blackbeard by Ace. And now with his parlay with the Five Elders…he even divided the community between the Shanks is good bro and the I don’t know he maybe up to something bad.
So…what do you think?
*Theory by Noctifago