If you are simply frequency counting you should use the 1:1 (~1 MHz full scale) THCAD setting to get the best resolution
The reason you do not lose resolution at lower frequencies (say 1:32) with a Mesa/LinuxCNC setup is that the THCAD frequency
is read via an encoder input and Mesa encoder hardware +LinuxCNC driver does n/t(n) velocity estimation which calculates frequency by counting pulses
_and_ the time between the first and last pulse per interval (not just pulses per interval) so its frequency resolution is independent of actual frequency