How does the flap configuration affect the tailstrike limit on the A320 aircraft family?
A higher configuration number indicates that the flaps/slats are extended by an higher amount.

In turns this means that for the same angle of attack the wings will produce higher lift (and drag) in the higher configuration.

You achieve take-off when the lift is at least equal to the weight of the aircraft, and with higher flap/slat deflection you will have sufficient lift even when the nose is relatively low on the horizon, leaving plenty of margin against a tailstrike.

On the other hand, if you are using a low configuration, the flaps/slats will be mostly retracted, and you will need a higher AoA to produce sufficient lift, meaning that you have to raise the nose of the aircraft more, leaving less margin against a tailstrike.