Find diagram showing the achievable framerates for 640xH frames for v1 and v2 camera here: https://www.raspberrypi.org/forums/viewtopic.php?f=43&t=2125...

Deal is basically "halve vertical resolution, and get roughly double framerate" (up to cap imit of around 665fps for v1 and exactly 1007fps for v2 camera).

In addition "tools/*_s" tools double vertical FOV while keeping the framerate.