You should get the 9" PX6 6 core unit. I had the older style fitted before (the 7" screen) but then I upgraded it to the PX5 8 core 9", which was a really good unit. I custom added a cooling fan because the processor did run hot but once I did that it was fantastic. Could easily handle all apps and I used to run waze + spotify on it concurrently with no lag. The PX6 is another step above the PX5. Fewer cores but much higher performance. It is essentially a quad core + a dual core processor. I had mine rooted and had viper running. Here is an example:
https://androidautoshop.com/bmw/386-2757-bmw-e46-3-series-9-touch.html
I did record a quick video playing around with the PX5 unit but I haven't uploaded it anywhere. I will if you are interested in seeing.
The only caveat is that it was a little annoying to install as I had to enlarge the stereo hole a bit in the car. I had to cut away the tabs with the factory screw holes in but all round it was a fantastic unit.