I've done a couple of scalloped bindings and I join the ends the same as on regular quilts, I just make sure the join ends up on one of the hills of the scallop.
However, I do not tuck the ends of my bindings, I think that looks sloppy. I join them on a 45°. Here is a video that best shows how I do it.
https://youtu.be/P1srfubwAIQ?t=135
Your binding strips need to overlap by the width of your binding strip. In other words, if your binding is 2 1/2", then overlap the ends of the binding by 2 1/2". If it's 2 1/4", then overlap by 2 1/4".