According to Splatoon wikia, Special Power Up improves the performance of special weapons, and for Bomb Launchers it only says:
Increases duration
So, knowing that Sub Power Up perk increases bomb velocity and travel distance, does it affects also bombs thrown while Bomb Launcher special weapon is active?
Best Answer
Sub power up does affect bomb launchers, but only under certain conditions. This Squidboard thread says it better than I can:
It will probably be more effective to use special power up because then you don't have to worry about holding R. You'll be able to get more bombs out, ink more turf, and it's easier to trap someone with your bombs if you're mashing R.