Since the mouse GUI only offers Acceleration and Acceleration Threshold (which is labeled as Sensitivity) there is no way through the mouse GUI to set the Velocity Scaling a.k.a. mouse speed.
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This works for me (and maybe for you too):
Where you see "Logitech M570" , fill in the name of your own mouse
you can find the exact name of your own mouse with this command:
xinput list
The speed values that I used work for me,
You will likely need to change these values depending on your mouse.
I have, in the GUI, both sliders on zero.
If, in the GUI, your acceleration profile is standard or adaptive, this probably will do:
speed="2.5"
xinput set-prop "Logitech M570" --type=float "Coordinate Transformation Matrix" ${speed} 0 0 0 ${speed} 0 0 0 1
If, in the GUI, your acceleration profile is flat you might want a much much higher speed
speed="500"
xinput set-prop "Logitech M570" --type=float "Coordinate Transformation Matrix" ${speed} 0 0 0 ${speed} 0 0 0 1
If you get an errormessage, then your mouse probably doesn't support "Coordinate Transformation Matrix"
You can examine if your mouse can do "Coordinate Transformation Matrix" with this command:
xinput list-props "Logitech M570"
if it isn't listed, it isn't supported.