In case of st, it actually delays the rendering. Its default config says min-latency is 8ms, and max-latency is 33ms. This probably is why OP got 20ms as an ave

In case of st, it actually delays the rendering. Its default config says min-latency is 8ms, and max-latency is 33ms. This probably is why OP got 20ms as an average value. The thing is that suckless people simply want to render less, and they have always kept a way to delay rendering in st. Also, the current latency is good enough that no one really complains. TBH, it's about 1~2 frame latency on 60 fps displays, and you hardly notice the difference.