Usefulness of high-pressure/high-volume switch on a track pump
Are you riding on Tubeless tyres?  If so, the high-volume pump can help to "seat" a tyre to the rim.  

Some tubeless-focused track pumps have a reservoir which can be charged with air, and then released in one fast PHSSSSST to "pop" the bead out to the rim and establish a seal.



Note they should not be stored charged, so its not like a portable air tank or a CO2 cannister.

I've never personally seen a track pump with a switch like you describe, but guessing its trying to be more things for more people.   A conventional floor pump will probably work fine for your bike maintenance needs.   Get an entry-level track/floor pump and go from there.