"Using "fixed tach location", will the speed of the intermediate shaft be changed proportionally based on the ratio added to the reference RPM? As I'm using a tachometer, will the software auto calculate the speed of the intermediate shaft based on the ratio?"
Yes. For example: Motor Reference speed is 1800 and Fan Reference speed is 900 rpm (0.5 ratio). Say actual motor speed from Tach is 1600 rpm (overwrites 1800), then fan speed would be scaled to 800 rpm when measurement is made.
No knowledge of the Pseudo Tach option. If someone has a 2140, then they could comment on this feature.