As far as fans go, you probably already know that you should only use a control switch specifically rated for fan control. Do not try to use a lighting dimmer switch to control the fan, you will likely damage the fan motor.
The only Z wave fan controller switches that I’m aware of all use the step system of low, medium, high. They do not provide infinitely variable control like a non-networked switch might. There are technical reasons for this that are not easy to overcome in a device that would be inexpensive enough for a home fan.
The GE 12730 seems to be a good device and a number of community members are using it successfully to control ceiling fans with low/medium/high.