Both expose the same API; Modern (1.9+) and Legacy (1.8) differ in internal mechanics, but your integration code is identical.
So your plugin does not package the stub. At runtime, the server uses the premium jar which provides the real classes.
Bow/Crossbow (weapon‑based) multiply based on the weapon. projectiles.arrows (entity‑level) adjusts damage/velocity/inaccuracy per arrow type. They can be combined; if you don’t want stacking, leave one at 1.0.
/damagemodifier debug next prints a breakdown of the next hit. simulate applies providers over a baseDamage only.