Okayu is right in that you'll likely be producing all the idols just like in One For All.
I said this before, but I named my group Nemurihime (after the manga Nemurihime with the unit Chihaya, Miki, and Haruka) in Im@s 2. And, I still named it Nemurihime as well in One for All.
In One for All, there are a lot of jobs using a 3 idol team. Even though you can switch out idols anytime, some people like to use their 3 most favorite ones. So, even though I named my team Nemurihime in One for All (where I'm producing all idols) my 3 highest level idols were Chihaya, Miki, and Haruka. So, I guess the name sort of works out if you look at it that way.
But, you can name it however you want. Usually, once you choose a name in the im@s games, you can't change it unless you start a new game.