@2mg I experience the exact same issue as you. The input lag in Crispy with uncapped + vsync on, but perfectly smooth in GZDoom. It's such as a shame as I would like to use Crispy, but I don't like the 35FPS experience.
For me, the input lag goes away if I use uncapped + vsync off, but then the screen starts 'warping' when I turn with the mouse.
Btw, I also experience the exact same thing with Doom Retro. It's possible to play for a bit and get used to the lag, but it's so much nicer without it, which is why I end up going back to GZDoom.
edit: Using different settings for VSync in the NVIDIA Control Panel and turning vsync off in Crispy produces different results depending on the setting. Some settings can make the input lag go away, but I still get left with the 'warping'.