Xaver Hugl, one of the KDE devs, wrote a wonderful post explaining triple buffering. Maybe check this out.

TL;DR (In the context of KDE Plasma) With all those changes implemented in Plasma 6.1, triple buffering on Wayland

• is only active if KWin predicts rendering to take longer than a refresh cycle
• doesn’t add more latency than necessary even while triple buffering is active, at least as long as render time prediction is decent
• works independently of what GPU you have