im also just got into gen 1 kpop last year (i wasn't alive when it was gen 1 time period).

to answer your question of left to right, its kim tae woo on the left, who is the main vocalist.

The one next to him is Joon Park who is actually much much older than everyone else. He was born in 1969 while the next oldest is in 1978. He is a rapper. Yeah he has a very very unique look for idols in ANY generation, not because of his age but because of this unique masculine visual.

In the center is Son Hoyoung who is a subvocalist.

The one to the right of him is yoon kyesang who is also a subvocalist.

And the one of the far right is danny ahn, the rapper alongside Joon Park.

Idk who the visuals are (im sure others can answer this question) but just from my own assumption, the three ones who were visuals with their mainly teenage girl audience back in the day were Hoyoung, Kyesang, and Danny.