How to determine maximum switching frequency of power modules?
The maximum switching frequency will be determined by thermal considerations. The linked sheet appears to be lacking good application information. Look at the curve at the bottom of the last page. That tells you that although the device is rated for 75 amps, 600 volts and 20 kHz, 20 kHz is the limit for 50 amps and 300 volts. That operating point is valid only at 50% duty cycle and with adequate cooling to maintaining the case temperature at 85C.

There should be additional curves to show the relationship between current and switching losses and other application constraints.