I am not sure I can put that fine of a line between coax and point source, several folks have made point source coaxial drivers Tannoy has done it for about 50 years, Thiel has been doing tweeters inside mids for a decade or so, Renaissance (once a Morel) has a high end coax. The difference between AAAAAAAAAA's point source and coax would be actual time alignment of the sound source in the speaker inside a speaker concept. for correct time alignment of sound, the tweeter should be behind the mid and the mid behind the woofer... I guess point source could be viewed as a sub-st of coaxial

In the Morel the tweets do not travel, their location is fixed in the magnets air gap

 

Your crossover frequency is also going to be an important factor. Higher crossover frequencies will make TA and position less important. I think almost any location can yeild good results if implemented properly. For my personal cars I generally put the tweeters on the same plane or above my mids. The tweeters frequency response helps to determine how much on or off axis you can install them. And your desired sound will help that as well.


I have never heard of a midranges magnetic feild effecting a tweeter.