So used Odin3 to successfully flash TWRP to the S7, without any driver errors.
https://samsungodin.com/

Rooting and TWRP tutorial - Samsung Galaxy S7 on Android Oreo
Downloaded TWRP file for device: Samsung
Check AP box in Odin, and browse to the TWRP file ‘img.tar’.
Before pressing ‘Start’:
See this video fior the trick to boot into TWRP:~
https://www.youtube.com/watch?v=5aE_AX8HBDg
NEED TO KEEP HOLDING Vol Up, Power and Bixby before and after pressing Odins Start, otherwise e-Recovery just appears.