As long as you have a 4th button your mouse that you can assign the Guard Break to, yeah. Or assign it to F on keyboard. Somewhere close. Changing guards is not an issue since all you have to do is a very slight wrist movement. I was very comfortable with the default settings for the block and mouse sensitivity.
I was playing the Ps4 beta first, then I downloaded the PC version.
Disclaimer: I have a mouse with 5 keys.
When I played the PC version I was thinking "Why did I ever play with controller?". For me, blocking with the mouse is so much quicker, easier and more responsive, blocking guard breaks was also much easier.
Just before the end of the beta I tried the PS4 version again and it felt slow and unresponsive, I couldn't block combos nearly as well as on PC.
The only thing that was easier PS4 version were deflects. A/D+Space is a little hard to time well