Hello, 

I have the option on the frontend to choose from different photo frames, but the position of the frame is not correct. If my understanding is correct, then I need to set the frame as the bouding box, right?

How would I do this? See image below for better understanding.

Thank you in advance!

You must create one FPD for each product variation. This is the best way

The better approach is to create separate FPD products for each photo frame and set up the bounding box accordingly.