Do you eventually get the option to have 3 of your puchased girls take the stage at the same time?

Yes. Most scenes require certain classes of clip for each position in the scene - e.g. pole dancers on the pole dance stages in that 3 stage scene or bikini clad models in a poolside scene. As long as your collection contains clips of suitable types to populate a scene then that scene can be used.

Also note that there are very many user created scenes out there - some simple fixed scenes and some very complicated involving complex movements, large numbers of perfrmers, and various special effects. To see those that have been posted to the forum follow the links listed in

https://www.istripper.com/forum/thread/42492/1?post=626142

この주제に関して見る事やデータへのアクセスは허가されていません。

which also provides links to a couple of web sites, one run by @wyldanimal and the other by myself, from which many of those scenes can be downloaded

There is also the forum thread for @smith2 's scenes

https://www.istripper.com/forum/thread/46600/1?post=694210

この주제に関して見る事やデータへのアクセスは허가されていません。