I guess is G3 is more aggressive than t cut, how does t cut compare with normal polish like
http://www.halfords.com/motoring/car-cleaning/shampoo-polish-wax/meguiars-deep-crystal-car-polish-step-2-473ml?_$ja=kw:skimlinks_phg|tsid:40392&cm_mmc=**********-_-PerformanceHorizon-_-skimlinks_phg-_-TopLink
Normal polish would be very mild, will only take out very shallow scratches - like you could probably make with your finger nail- unless you spent ages rubbing the same spot or used a electric polishing mop.
Think of it like sand paper, a very fine sandpaper will get you down to bare metal, but would take you a while ( normal polish) but a corse sand paper (g3 say) will get you to bare metal much quicker with less effort, so tcut would be like a fairly fine grit sandpaper.
Obviously none of these are like sandpaper, but hopefully it gives you the idea of how abrasive these cutting compounds are or not depending on which you use, and there are lots of different ones.
Strangely though the lacquer on the Leon seems very hard (yemv) I tried removing some out of my old leon, even with g3 and a mop it took some doing, so you might find, depending how deep they are that you won't even dent then with normal polish or tcut, especially by hand