Chain Lightning would visually suit the Titans, while the Storm Riders need something more...airy... but I can't recall anything similar that would fit.

If so, should we swap the visuals? Because, based on the name alone, it makes sense for the Storm Riders to throw lightning, but it's not necessarily a must for the Titans.

And it would be a shame to take away the Storm Riders' ability to shoot, the animation is beautiful.

For some reason, I thought they and the Titans had the same animations...

and it's unlikely that anyone will use it, because ranged units are usually prioritized over melee units.

Players of the League disagree with you.
The logic with the Titans is simple: they are a tier 7 unit, and also a large creature, which are not the best ranged units. They are easy to take down, they have a lot of health and defense, which allows them to effectively tank. If you increase their stats or give them a good melee ability (a stunning blow? Maybe a cast of some kind of spell on hit, like lightning? Although I'm not sure if that's feasible), then it would more than compensate for the ineffective shooting in this case. Another upgrade, with shooting, would be taken under certain circumstances: a general focus on shooting for the mage, capturing/defending cities, and so on, which are also possible uses.

Option 1: at the NONE level, give a knockback of 5-10% to highlight the Hive as not just a damage spell, but also as a control spell.

I like it.