Just have a look at the wingtip on your PA28 next time you fly. Stand by it. Look at the distance between underside of wingtip and the ground. Now imagine the aircraft banking whilst maintaining contact with, lets say the port undercarriage. Now imagine how steep a bank angle would be neeeded to scrape a wing.
There's not a chance! I even doubt there would be sufficient aileron / rudder authority to enter a 'slip' (not merely back) at the low approach / touch down speeds.
Re maintaining the centre line, practise, practise, practise. Try practising on a long runway with clear centre line markings, so you don't have to worry about correct touchdown point for time being. It will come....!