Do the Double Shot and Bloonjtsu upgrades pierce more bloons?

Question

The upgrades increase the number of shurikens,
so do they pierce more bloons, add more popping power, or both?

Answer 1

Each projectile can hit up to four bloons (the Sharp Shurikens tier two upgrade), reducing each by one layer. So a 2/* can reduce four bloon layers total across four bloons. If it hits just one bloon, it can only reduce one layer. Same thing for two or three bloons is two and three layers respectively.

A 3/* (Double Shot) can reduce up to eight bloon layers across four to eight bloons. I.e. each projectile can hit up to four bloons and a given projectile can only reduce a bloon by one layer. Since there are two projectiles, together they can reduce a bloon by two layers if both hit.

A 4/* (Bloonjitsu) can reduce up to twenty bloon layers across four to twenty bloons. Again each projectile can hit up to four bloons and only reduce a bloon by one layer. This time, there are five projectiles which can reduce a single bloon by five layers if all five hit the same bloon.

They have much the same impact as an increase in popping power if they hit the same bloon. Or the same impact as pierce if they hit different bloons. But they work by increasing the number of projectiles rather than increasing popping power or pierce.

Answer 2

This upgrade means that more shurikens are thrown, so it can pop more balloons at once. It doesn't pierce through more balloons.