See this in that way:
Totland cover over 30islands, each minister take the role and protect them, adding to the ministers Big mom lead a huge fleet and every Minister have his own battleship together with a fleet if he needs help. Big mom tell us reader that it take many years since Cracker,Smoothie and Katakuri meet each other. They are protecting their own island+taking down other island as we see in chapter 827. The enemy with Perospero face aren´t the same as the one who Smoothie face, Smoothie have a totally different territory and her own mission to protect totland. So it make sense why Smoothie face different enemies and kinda don´t know King while Pero knowing King more(at most Pero is also the first son who probably clash with many strong pirates) then anyone else, same for Compote she know King while Mont-d or didn´t know him.
The reason why Smoothie probably know Marco is that she meet him during a battle?
When someone invade Totland, the Sweet commander protecting their territory, Kid,Apoo and Urouge probably face a different Sweet commander overall. If someone attack from the territory where Smoothie island is, she gonna deal with the enemy, if someone invade Snack territory, he gonna deal with him.
Big mom has a huge army and their children know very well to protecting their territory, so a war between Yonkous in the past doesn´t surprise us, it was also said in the novel and it make sense.