What it boils down to the lower the tau value, the faster the coupled parameter is pulled towards it’s reference value. It needs to be low enough such that the value doesn’t deviate away from the target value, but high enough so that it allows the system to respond to fluctuations not too harshly.
You can see this occurring with the two graphs you have shared, low value on left pulls the pressure (and hence volume) back towards the reference value quickly, high value on the is much slower.