Very good question; I'm no expert by any means but here's what I understand:
There's a two-fold benefit to co-witness irons.
1. If it's a Defensive pistol; and you draw only to find the red dot is out (electronic or battery failure) the co-witness is your back up sight. In a pressure situation you have the confidence the irons will be there no matter what.
2. The irons serve as a reference to help you bring the red dot into the picture quickly. Eventually, you'll develop muscle memory, and just bring the gun onto plane with the dot.
If it's simply a range gun; and target acquisition time is not important; then co-witness is not important. Springer and others also make mounts for CZ-75's, and there are other good optics like RMR's, Leupold DP-Pro, Burris Fast-Fire, Vortex, etc, etc. but generally the combo of mount and optic they sit much higher. But, they may also have advantages over the JPoint and the price goes up accordingly. YMMV I'm simply trying to offer a good cost-effective starting point.
I will say this; once you get used to a red dot; you can acquire and hit multiple targets so much faster. You are looking through the 'window' with both eyes fully open not squinting, placing the dot quickly on your target like a laser; so your peripheral vision is fully engaged seeing the next target(s) or other threats in the room. Especially beneficial if you have old eyes like mine.
In any event; co-witness or not; this particular JPoint red dot and mount set-up is still relevant and cost-effective on a CZ 75 even if you choose not to use the co-witness front sight. If for some reason you don't like the red dot simply remove it and you haven't milled up your slide.
Hope this info helps.
P.S. On the benefits of pistol Red Dots, I defer to much more experienced CZ administrator/members like s0nespark who uses one on his EDC P-07 or Joe L who uses one on his Bulls-eye CZ pistols shooting 100 yard targets lights-out. Joe L's bulls-eye videos blow me away!!