It is possible the app is restrictive regarding the overlap you choose, because such a big overlap (<8° between images) can greatly increase flight time. The fact that the issue disappears when you increase the overlap value points to this.
Could you try planning a very small circular mission and set the overlap to less than 8° to see if it works?
Keep in mind that the Bebop 2 drone has a fisheye camera, meaning a very wide field of view. For this kind of camera, the overlap between images is very large by default and you should not need to resort to such small overlap values.
Regarding the basemap providers: they are different for Android and iOS, which explains the different zoom capabilities. If you feel you have trouble accurately planning your missions on iOS, do you think being able to import .kml/.kmz files would help you?
You can follow and comment on this thread where other users are asking for this feature. You can also read about this feature that we have already implemented on Android here.
Indeed, the minimum flight height is different for Parrot and DJI drones. The reason for that is that the Parrot drones Bebop 2 and Bluegrass are safer to fly, so we allow a lower flight height.
Finally, do not hesitate to create a new post if you do not find any topic related to your question on the community.
I hope this helps!