Wow, thanks for all the helpful feedback! Are there any concern about the Canyon frame being too tall? I did notice that the reach and stack on that bike is considerably longer than on P5/P3. Also, what exactly do you mean by limited adjustability on the P5. As far as I can tell the only thing I couldn't adjust is then tilt on the aero bars.
The P5 is difficult to make small adjustments in stack height on. There is a 50mm jump from low to high V, changing steerer spacers is a pain because the hydraulic cables run through them. The pad width ranges from very narrow to quite narrow, not many first time tri bike riders find that optimal. Superbikes are for when you have your position dialled and will not be making changes. You will get more benefit from having a bike that is easy to adjust.
The Canyon is actually very similar in reach/stack to the P3 for most sizes (I've lined up corresponding sizes below)
Obviously the 48/51 and XS/S don't match up as well as the larger sizes.
You get more options with the P3 and more versatility - you don't really want to use any stem other than the speedmax one for that bike as it matches the Bento box. P3 you can grab any stem and find a bento to suit.
All that aside, it sounds like the first thing you need to do is get a fit on a fit bike, get the coordinates of your position - then find bikes that match. It may be that your choice is a different set of bikes to the ones you're currently thinking of (though this isn't that likely - P3 will fit most people)
Connect - Velogic Fit
Or - Speedtheory