In terms of pitch geometry limits there is absolutely no difference in tailstrike clearance between flap settings. The tail will scratch the ground at the same angle.
The question is what pitch and speed (AOA actually) is required to support the lift you need between flap settings.
You will need more pitch and speed in a conf3 landing to arrest a downdraught or a high rate of descent close to the runway. Thus you cannot ask for this pitch comfortably as you would with conf full. This is how you become somewhat limited.