I don't why you would do this or how far it would stick out, but consider the following:
The front facing radar is behind the Mazda logo. Knowing what it used for, it shoots down the road more or less parallel to the ground. So that should not be an issue. But if you want to test for obstruction you can. Per the manual, "The Mazda Radar Cruise Control with Stop & Go function (MRCC with Stop & Go function) system is operating, a single beep sound is heard when “Front Radar Sensor Blocked” is displayed in the multi-information display." If you already have the hardware you could put it on and try it. If not, I suppose you could could do something like putting a box or other object on the ground taking up the area where the hitch would be, then engage MRCC with Stop & Go and see if you get the warning. You could go crazy with it by covering the radar first just to be sure the warning function is working in the first place.
The front facing camera at the top of the windshield is also not a problem. It shoots down the road and even if it didn't it's pretty clear it's line of sight is obstructed by the hood until several feet in front of the bumper.
That leaves the other front camera. In one place in the manual it says it is in the bumper; a diagram shows it next to the logo, which does beg a question as to where it is exactly. In any case, the only thing the manual says it is used for is the 360 View Monitor which agrees with a diagram showing it pointing down directly in front of the vehicle. I don't have the 360 view; somebody who does might see evidence of where the camera happens to be. I don't know without looking it up if your 2020 GTR might have this feature. If not, no issue. If so, the installation of the hardware or the box test is easy enough to do by just looking at the 360 display.