While you're correct about the MCU not doing direct adaptations and that we should keep our expectations in check, there are also factors that were involved in their decisions with Wanda and Pietro that don't really apply to the YA characters: the reason why they HAD to give them a different origin is simply because, at the time, Marvel Studios didn't have the rights to use some of the key elements of their backstory in the comics (mutants, Magneto, etc), so they pretty much had no other choice. But then you cut to 2021, and you see that the team behind WandaVision tried their best to bring Wanda as close as possible to some of her comic book elements, even retconning her previous origin by revealing she always had magic powers. And of course, giving her a magical pregnancy, which was very important to the Young Avengers later on. So even though they don't do direct adaptations, they did adapt this particular story in a way that easily allows them to be more comics accurate in the near future.
As for Teddy, there aren't really any legal issues regarding what race he is supposed to be. Marvel can freely use Kree and Skrulls. So even if they wanna change the identity of his parents, which would be understandable, I think keeping him as a Kree/Skrull is important enough to his story and easy enough to do that there isn't really any reason why they shouldn't do it. So yes, I can see them changing some details and overall context, but I think they already have the perfect set up for those characters and it would be very weird not to use it.
My understanding is that their story happens to be one of the arcs of an anthology series called ''Love Unlimited'' that's being published right now. Much like the Paradox Lost Young Avengers story was the second arc of another anthology, which means we're only getting the Wiccan/Hulkling story after whichever other arcs wrap up first. I don't think they mentioned when that is happening, though.
But speaking of this comic, it's kinda funny thinking they made Agatha be the ''villain'' in the first part, knowing what we know now about Billy and Teddy possibly being in her show. I wonder if it was just a freak coincidence, or if it was a rare case of early synergy happening.
It's not like his origins need to be addressed at all in Coven Of Chaos, to be honest. The casting call says ''Tyler'' is one of the leads and ''Patrick'' is a supporting role, so that probably means Teddy would only be there for Billy's story, which would likely be the bigger focus.