You should be okay. The important thing you need is the engine tacho feed for the RPM display. The Digifiz also requires the RPM feed to be a low voltage digital signal, as opposed to the signal you’d normally get from the coil negative, which is usually very ‘spiky’ due to the coil inductance. (The Digifiz gives an erratic RPM display if you use this, so on a normal 8V / 16V Golf MK2 you would use the input trigger signal that drives the coil amplifier unit).
However on a 20VT you have separate coils anyway don’t you. Does the 20VT ECU provide a tacho signal on any of its pins to drive an instrument cluster? A quick Google suggests that the 20VT ECU has a tachno output wire, which people usually use to drive the analogue cluster, which would be ideal. Haven’t any personal experience of this however.