2) Z-Girls was a seven member group with each member from a different non-Korean country. For me, Streets of Gold was a bop, but overall they had limited success. Officially they still have 3 members but I'm doubtful they'll release any more material.

(G)I-dle is definitely the most successful majority non-Korean kpop gg even based on Last Dance alone. If you include bg's, of course there is NCT but they have a very different and non-traditional structure, idk if you can really compare them.

1) and 5) I can't predict how well the new music will do, or what it will be like. I do think it is a critical time for them. In my opinion Soyeon will do well to not necessarily be in control of every song; outside songwriters and producers can help give them a fresher sound with more variety. I do think we will never see G(I)-dle go the "cute" route (god I hope not). But I'd like to see some of the girl crush, and dark and moody aesthetic tempered with some wholesome, positive vibes (like Help Me was).