There are morphs readily available for the Genesis figures. They do give you breast sliders. But there are a ton of breast morphs depending on whether or not you want them natureal, silicone like, or just plain crazy-sized.
That said, you don't actually get DAZ and then in two days start making a game. I have played with DAZ for years and am getting to know Unity a bit, and I am still unsure as to actually how to make the characters behave right in Unity.
At the very least, go check out guides en masse. And get some reading material about Unity.
If you just want to use it for 2D renders, I wouldn't bother. TK17 is easier and faster to work with. Also, you will need months or years of playing with it if you want to avoid your characters looking like those in half of the other DAZ-character games in here.
But, good luck with it
