You can get a softer plastisol print by using an additive like Wilflex Fashion Soft. You can add this to your plastisol inks and they will flow better, and print softer. The ink will not be as opaque though so keep that in mind.
Discharge is possible on garment dyed items, but be aware that it will be harder to match colors and the the discharge effects may be unpredictable. You should definitely run some tests before committing to it.