I mean it also depends on the power and structure of Fae in general. Kringle must kiss the ring, but Vadderung can tell her to get in line. Games of protocol are how they show respect. Erlking, Kringle and Eldest Gruff had to show face at Harry's first birthday as Winter Knight an official court event. In contrast in changes Erlking warns Harry not to summon Mab to his hall where he holds domain.
WOJ touches upon it.
Dudesan: You've described Santa Claus as being the Winter King. What does that title mean? Do Winter and Summer each have a trinity of Father/King/Prince, like they do with Mother/Queen/Lady? Is the King necessarily the consort of the Queen? If so, will we be seeing Oberon at some point?
Jim: 5) The Faerie realms just aren't that structured. It's more accurate to say that he is /a/ Winter King. Or even more accurately, that he is a free Wyld Fae who is of a power level that is on par with Mab's and happens to neighbor her sphere of influence, and finds it simpler to show up to family dinners during the holidays and make polite than to start staking out boundaries and establishing treaties.
The kings are sort of the opposite of the queens in their given season. They are independent of their Queen’s courts. The Erlking is a summer king and he is not a particularly friendly guy, whereas Santa Clause, one of the winter kings, is kinder, the spirit of generosity in a time of bleakness. Yah I’ve gota have Harry ask Mab about him so she can roll her eyes.
Erlking is also in Mab's class. The Erlking (who isn't Cern) is a being of Faerie who is in Mab's weight division, if not her equal.
Erlking is also specifically stated as independent of Mab and both courts.
There is no such thing as a Summer King in the Dresden Files faerie cosmology. Mab and Titania need a King like a fish needs a bicycle. :)
There are a ton of independent rulers of the Wyld, though, much like the Erlking, who is a member of the Winter Court more or less as a sign of courtesy and respect. They will occasionally make alliances (and dalliances) with the great rulers of the Sidhe.
WOJ is that the Erlking could theoretically create his own Knight albeit less powerful the Summer or Winter Knight
longshotauthor is it possible for the Erlking to create a Wyld Knight or some equivalent?
@SuperSnapper61 Engh. He could feasibly take a part of his own power and fashion a new mantle from it. Much weaker than the WK though.
@den_down_unda @jim_turnage The Erlking is simply not on the same scale of power as Mab, though he could probably hand Molly her head.
Plus WOJ several time has said that Harry tends to judge things about who would win in an outright fight, but it's suggested or stated that beings of power play on several levels not just fights.
Your question presupposes a linear hierarchy--which isn't surprising, since the series has come from Harry's viewpoint, and Harry is a straight-lines kind of thinker. Power is a much more nebulous thing than that, and something that is problematic to quantify...