Sony series is not Mac Compatible. What are you wanting to do that iMovie cannot do? Ask yourself this first. Is iMovie the limit? Have other iMovie users ran into this problem? Did they work around it?
Editing basic cuts isn't difficult. Multiple tracks, syncing sound, and key frames starts getting challenging.
FCP X is the cheapest of the "Pro" software. It is the most like iMovie in use, so it will be the shortest learning curve for you.
Adobe is the most popular for semi-pro-sumers, but $50 a month turns into $300 fast. Part of that popularity is piracy. IF you are getting paid for your work, you don't want to get busted using pirated software.
Hitfilm Express is free, and more powerful than iMovie. I find Hitfilm a bit more difficult to use than FCP X.
As far as it goes, you have a $400 camera on a $1000 drone (plus any other cameras and lenses you shoot with). Going cheap on the software that processes every single shot you take may not be the best move.
Oh, forgot to mention above, I correct my GoPro lens distortion in GP Studio before import into FCP X. The only way I know to do so in FCP X isn't as good. Someone is working on a plugin, but I haven't seen it yet.
Edit - Which reminded me to go looking and found a plugin to correct wide angle distortion at Alex4d.com -- free.