I was referring to the most important characters you'd want in your team: Ganyu for cheesing almost everything, Zhongli for shielding vs everything, and Venti for sucking up everything so that the first one can cheese it. If you have these three you can do virtually anything (well, maybe except 36* Abyss), even if they don't bring massive reaction numbers that are possible under Morgana or National Team. Though I suppose Bennett should be there too, heh.
My 4* policy tends to be "if I can get them, I'll add them". Before Yan Fei I pretty much had every one of the 4*s, so I'm looking forward to adding her in Ayaka's banner despite already having C6 Chongyun and Ning. I did edge quite a lot in the past, nabbing Sucrose close to pity, Xinyan during Zhongli's banner, etc. Some Reddit discussion points towards the new bow being not quite as good as Crescent on Ganyu, though some prefer the less conditional powers instead.
I ignored the islands for the most part; today I just finished the homecoming seelie and the mural quests. I've cleared out the first two archon quests (finally letting Dain leave Andrius, and meeting Aether), going to finish Atsuko, Kazuha and the rest before the maintenance tomorrow. As for Inazuma, some say that it's possible that we can see it from Guyun, since that's the southeastern-most section leading to the islands. It'd be fun to see the old unrendered islands, then load after maintenance into the newly rendered ones, something like how Dragonspire was just some 2D images before its update hit.