How to stop phone app from full screen overlay when receiving a call

I use a third party app for navigation. My car has a bluetooth connection to my phone. When I'm driving in an area I don't know, and I get an incoming call, my display is completely overtaken by the incoming call answering screen. This is disconcerting and potentially dangerous. What I really want is for my phone to figure out that:

1. I'm in the car, i.e., a particular bluetooth connection

2. Don't overwrite the my current 3rd party maps screen with the fullscreen Phone answer screen. Just give me a top-screen notification and I can then choose to answer it or not answer it via my car phone button.

I would think this question would have been asked, if not answered, but I haven't found it yet. Changing the Notification style of the Phone app in Settings doesn't change the behavior.

Thanks for any info people can give me.

Regards,

Anthony