Personally speaking the "drama" at the end of season one was perfectly done. [SIP spoilers]Obviously the characters weren't acting rationally, but you have to consider that they are not the wisest people on hearth. Also, the "We are about to disband" trope is pretty common, but the excuse here for this problem to happen was in fact well done. Kotori had an actual reason for not telling Honoka, and Honoka, who never cared for idols, obviously lost all motivation do to continue. The fact that the Love Live grand even was skipped for me was a huge plot twist: I expect the MCs to be always on the winning side.

As for the resolution [SIP spoilers]It was quick, I agree, but it made sense. Kotori wanted to stay but nobody was telling her so. Only the "selfish" Honoka could, and that was the source of the entire drama early on: Kotori always wanted Honoka to stop her, but she never could tell her. So, all it took was Honoka to do the (right) thing and prevent Kotori from leaving: everyone is happy.

I also agree that the second season ending was built differently but very well done non the less.

As for the remaining shows here's what to expect:

• Sunshine = pretty much what you liked in SIP, but better production value overall (animation/drawings...). The story is different of course, but it's not that different. As I say often: Sunshine and SIP comes from the same mold.

• Nijigasaki = Totally different style, composition, everything. You are going to ask yourself if this is Love Live or any other idol show. Non the less, tons of people like it. Enjoying SIP or Sunshine does not make you more likely to enjoy this.

• Superstar = "back to the roots" with some differences. It's much more the usual Love Live, but with some elements retained from Nijigasaki. If you enjoyed SIP/Sunshine it's highly likely you'll at least enjoy some part of this.