The hiss sounds like some induction coming out of your PC (power supply, CPU, graphics card). I have heard this kind of noise a couple of times when using cheap USB sound cards. Maybe you can hear some changes moving your mouse or opening/closing windows on the PC.
I will provide here a kind of automation for the editing of sibillance in a vocal track.
I will not cover any specific program cause every program is a bit different but generally I'll be talking about industry standard programs like cubase/studio one/pro tools etc..
Add a gate to the vocal track. That gate should band pass all the other frequencies and ...