Like all of this mod's sentries, it benefits from both the player's sentry speed and sentry range stats.
Its best Modifier is Ruthless. The Mythical modifier provides the widest array of stat bonuses, but these primarily affect the initial summon rather than the sentry's damage. Additionally, sentries cannot deal critical hits under normal circumstances. The only significant advantage a Mythical Bubble Turret has over a Ruthless one is knockback.