Difference between multiple arrows & split projectiles?

Hi all

I'm new to PoE2. Playing it co-op with a mate and we're loving it so far!

I'm using a lightning ranger for my first playthrough and wondering what the difference is between "Bow attacks fire x additional arrows" and "Projectiles split towards x targets"? Let's say x = 2 and both hit... is the damage of each hit the same for both modifiers? Or are they calculated differently?

We only just finished act 2 of the campaign and I haven't scored any unique bows yet. Using a rare dualstring atm but I noticed some of the uniques have projectile split and I'm curious how the math works.

Cheers