Overall warlords and as many have underlined they were better in the pre time skip.
You had Doffy who is one of the best characters in the verse, BB was a part of them for a period too (he will eventually leave the yonko group too but it is right to consider him part of that group), Hancock was well characterized as well, Croco and Jinbe too, Moria is another good and tragic character if we are talking about One piece. And they all fit the concept of warlords (corsairs) who fight for the WG in exchange for something in return. Mihawk was never really characterized like the others but mystery is a big part of his charisma. It was even interesting that people joined and left these ranks after old members were demoted. Yet at this point even if the warlord system is officially dead they still live and are all recognized as warlords.
Admirals for me seem almost 1 dimensional: dudes 3 meters tall who have different concepts of justice and a powerful df (usually a logia). Aokiji has shown some characterization when he collided with Akainu, left and joined BB but the others are still scarce, Kizaru recently has shown something but in the end he sacrificed his friends (and what was left of his soul) to follow the orders he was given, but at least he actually felt that. I don't know if overall is a good or bad thing. They also have good and bad moments (Akainu donuting Ace and Greenbull introduction) but at this point I doubt you can really expect something from them. Aokiji will eventually betray BB but it seems the others will be loyal to the WG until the end (if Akainu doesn't pull some SWORD twist at some point), GB will stay loyal as well (only chance is that he seems a diehard fan of Akainu and if Akainu betrays the WG then he could follow). Fuji is the odd one among the admirals, he will side with Luffy when the time comes.
Yonkos are weird too in a way, while warlords actually feel like corsairs (everybody is there with the WG to fain something, they have all their own agenda) the yonkos are similar yet different. They are like the super powers of the OP world but still below the WG, they have all the same agenda of absolute dominion over the others (bar Shanks) and tried different roads to get it. That was even good but BM was turned into a clown and that ruined the whole category in a way. They were also screwed by Luffy and unfair plot power, they basically weren't allowed to defeat Luffy by plot and eventually (Kaido) had to face a god reincarnate who can reality warp. At that point the yonkos as a group were already destroyed (at least as they were originally meant, scary tyrants of the new world) and instead a new yonko system was build were we have the child of the prophecy, good guy Shanks who keeps doing nothing really relevant until BB eventually kills him.. aside from traffic control (Marineford and pest control with Kidd and GB), BB who is still cool with the original idea but he superseeds the yonko category like he could not really be considered a warlords as well, he has his super villain plot he is executing since his introduction. And finally Buggy who killed the category even more by becoming a de facto yonko joke (unlike BM who at least is not fully presented as a joke by Oda but only most of the time).
Supernovas are filler. They were a cool concept during Sabaody but it was clear only Law and Kidd could possibly be rivals for Luffy (until they were inevitably turned into cheerleaders at the end of Wano). Anyway they have cool powers and even personalities but now they are just dropped sparsely in each arc so that they can cover some space but in the end they all failed in their pursuit of power (maybe Law or even Kidd will be an exception somewhat, and in a flashforward Oda can throw any weird idea he likes like Capone an emperor etc. but that doesn't count).