I don't know what you get for slow, medium and fast. With a 90+ furnace they usually recommend the longest cycle rate for efficiency. You can always experiment.

 

Experiment? That would involve purchasing it, having it hooked up by a professional and then possibly finding out it's not what i want. I posted this post to avoid just that but thanks for the input.

 

There is no fixed swing differential - that is a common feature of cheap, low quality digital thermostats. Better quality thermostats like the Sensi use a much more advanced, P+I algorithm that continuously recalculates the swing differential to meet the cycle rate setting at your current load.

At a given cycle rate setting, when loads are low or if your system is oversized, and meets the setpoint quickly on each cycle, the swing differential might have to be quite large to keep the equipment cycling too much for the setting you picked. Other the other hand when the equipment is running a larger percentage of the time, it will be able to give tighter temperature control.

Keeping all other circumstances equal, a higher cycle rate setting will give tighter temperature control, at the cost of being harder on the equipment and (potentially, depending on the equipment type) leading to lower efficiency. You want to pick the lowest cycle rate that keeps you comfortable.