I'm attempting to build this amp I got from runoffgroove.
The problem is that the capacitors have no units so I don't know which to use.
Are all the capacitor units in µF?
Yes
Is this a common practice?
It is very sloppy to not give the units.
As for the volume control on the output, this is a musical instrument amplifier, likely for an electric guitar, that is meant to distort. So the idea is probably to set the Gain control to get the amount of distortion you want, but be able to change the output volume without giving up distortion.