Perhaps Creator God is just the most powerful have a powerful race of spiritual beings.
It would be easier to explain this if I used us as an example suppose you have a great artist that creates a magnificent painting. Then you have other people who are of the same race as the artist but don't have his skill. They still have some skill maybe almost on a level with artists others could barely make stick figures. The artist in this example is your Creator God the painting is the universe and everyone in it and the other lesser gods are everyone else. Overtime the other gods might become interested in our universe just like we would become interested in a painting that someone else made this might create a conflict between God creator and lesser gods as he might not appreciate their involvement in something he made. I'm not sure if I'm explaining this clear enough.
Answer to question 1 in this example your lesser gods would would be of the same race as your Creator. So whenever origin story for him with parallel there's. Except for the creation of the world of course.
Answer answer the question 2. Depends on the God but I assume that most would want to Explorer the universe and interactive humans and other created creatures maybe even doing things to them see how they react. Depending on what they do they might find themselves coming into conflict with the Creator God.
don't understand question 3 could you try to explain?
Okay to answer your questions. First let me divide the minor gods. Into major and minor among themselves. They'd all be minor gods in compared to Creator God. But They probably would also have hierarchies among themselves. Among their own hierarchies if I were you I would follow the example and in most mythology and have 12 major or ruling gods and hundred or so minor gods who are mostly aligned with one of the 12. But that's just me you can follow any mold you like determine the number of lesser duties.
As for their interaction with mortals, since they did not create this world I can see most of thier interaction come from sheer curiosity about this new creation. For example they might appear for a large crowd and demand worship not because they care what mortals think of them, but because they are curious as to how the mortals will react when they do. Curiosity however might be kept in check by their Creator God .
I could easily see these lesser gods coming into conflict with Creator God. They might for example introduce an idea into humanity out of curiosity to see what they will do with it. But for whatever reason this idea runs contrary to whatever plans Creator God has for his creation.
As for why they are here as soon they would be interested in us just like we would be interested in a master painting like the Mona Lisa especially if these lesser gods had not managed to create a universe on their own or ifbefore the creation of our universe they had tried to create a universe on there but failed.