You can switch between modes using the +speed_throw keybind (usually right mouse key).
Initial mode will be 0 which is "full rotation" without any limitation.
1 will then be "limited rotation" which allows for more "default" rotation like "just left"/"just right"/"just forward"/"just backwards" or "just down"/"just up".
2 is only accessible through the +frag keybind (usually G) and completely locks the current angles.
Icedream