Will Samsung Fast Charge charge a QC 2.0 device as I have seen that Samsung phones can fast charge on both Qualcomm Quick Charge  and  Samsung Fast Charge adapters.  

But I am unclear if you want to charge a HTC/Sony etc Qualcomm 2.0 device if the Samsung Fast Charge chargers will charge the device similarly to a dedicated quick charge 2.0 charger?
Yes, of course.
Samsung Fast Charge is basically an alias for Qualcomm QC 2.0/3.0 (for S7/S7 edge). They are totally compatible with each other.