I am wondering whether one could cast Storm Sphere as an action, and in the same turn immediately follow it up with the spell's bonus action to deal more damage.
I have a feeling this doesn't work, going by the PHB's rule on bonus-action spells (emphasis mine):
A spell cast with a bonus action is especially swift. You must use a bonus action on your turn to cast the spell, provided that you haven't already taken a bonus action this turn. You can't cast another spell during the same turn, except for a cantrip with a casting time of 1 action. (PHB, p. 202)
But I wanted to check and make sure, in case there's a slim chance the wording intends to mean if you begin a turn with a bonus action, you can't follow the bonus action up with a non-cantrip spell.