Actionable advice from the article: Using Wayland natively from Wine does seem to help, especially against latency jitter / for consistent frame pacing, which is a typical improvement for Wayland.
It's likely his monitor. Would be interesting to see CRT results.
A lot of people still seem to buy their monitors without considering latency, which majorly sucks. It feels like the years between power supply efficiency making a difference and the introduction of 80+ efficiency standards.
"To investigate, I used a small Teensy microcontroller to measure click-to-photon latency. It acts as a USB HID mouse and is paired with a light sensor pressed against the screen. I flashed it with an existing Open Source LDAT sketch, with slight modifications. The resulting setup can log hundreds of samples to a CSV file, unattended."