Is it a fit issue?
A road bike with the same length top tube / stem as a hybrid will have a longer reach due to the drop bar hand position being forward of the handle bar.
As a joke, I put drop bars on my mountain bike, way too long a reach for me.

A change to a flat bar will shorten the reach as will a shorter stem.

A fun project, and a good learning experience.

Over the long haul though a drop bar bike is faster, in respect to the fact that in the drops you're faster over long haul being more aero.

Changing the bar / shifters will also require finding brake levers for caliper brakes, rather than V brake levers, putting V brake levers on caliper brakes would provide too much cable take up. meaning that the levers will over power the brakes, and that's not good. So make sure you get proper brake levers.