technically it's the vacuum modulator that controls the shift quality. the bowden cable adjusts the shift points at part throttle which may cause a feeling of abruptness / harshness in the shift if for instance the upshift point is too low. check this thread out for correlations of upshift / downshift while adjusting the bowden cable:
http://www.peachparts.com/shopforum/showthread.php?threadid=28537&highlight=downshift+bowden