So since I got the Keychron K2 Pro and NuPhy Air75 in my hands right now, I decided to compare latency with my Logitech G915 TKL using an online reaction test.
https://faculty.washington.edu/chudl.../redgreen.html
G915 - low profile Kailh Choc blue
K2 Pro - Keychron K Pro brown
Air75 - low profile Gateron blue
The G915 TKL with the wireless Lightspeed dongle is my point of reference. It's how I normally use the keyboard.
Pretty amazing how the G915 on wireless is faster than the other two keyboards wired.
Under normal usage, I would say both the K2 Pro and the Air75's latency was indistinguishable compared to the G915. The only time I noticed a clear delay was with the Air75 in Bluetooth mode. Not sure what's going on there.
I haven't tested these under gaming conditions, but I imagine the results will be similar.