Can't say I was missing Stingray, but I was surprised, and a tiny bit disappointed, but the complete absence of Aisha. (I think she gets mentioned all of twice?) It felt like a part of the show is missing, but as I understand she's supposed to be in S4.
Demetri and Hawk were pretty well handled. I'm not sure I buy how good they made Demitri in a fight, but otherwise, good stuff.
Them showing restraint and not doing love triangles (other than the kids, of course) was admirable. I was so sure they were going there with Kumiko, but no, Daniel-san gets some much needed perspective and encouragement, and then leaves. Good stuff.
Tori....is less of a psychopath than S2, and that's a good thing.
Sure seems like Terry Silver is coming. One thing I LOVE about this show is the use of archive footage. You were right, you really DON'T need to watch the movies to get the story. The only thing you get there you can't get here is Mr. Miyagi, but admittedly Mr. Miyagi is the man.
And of course, to quote Alfred Hitchcock "they don't go to the police because it's dull." (And the one time they do, it doesn't work)
The kids giving a speech about the power of friendship karate is more schlock, but you're having such a good time at that point you can't bring yourself to knock the show for it.
Yeah, Kreese is the "Negan" of Kobra Kai. You get context for him, but you really don't get any kind of justification.