Things that slightly bother me

I was re-watching Revenge of the Sith the other night when I noticed a few technical problems with some of the weapons shown in the movie during the initial battle.

First, the buzz droids. I suppose there may be a psychological warfare aspect to a missile that explodes and scatters small robots that slowly tear your ship apart, but really, wouldn't about 10 pounds of high explosive work just as well and leave less time for countermeasures?

In another scene we see a number of battle droids firing several large energy weapons. These eject a shell after each time they are fired, similar to a modern artillery piece. My question is why there is even a shell since it is an energy weapon? A shell serves to hold a propellant charge for launching a projectile. An energy weapon wouldn't strictly need one, and it would be best to avoid having one, since most of the hard work for a modern artillery soldier is the task of lifting each shell from storage into the breech of the gun.

Also, why is Mustafar consistently called a planet when it is clearly a moon orbiting a large gas giant? This system seems to be based on Io, the innermost of Jupiter's large moons, which is heated to extreme volcanic activity by the gravitational effects of Jupiter on the one hand and the three other large moons on the other. I suppose for the purposes of the movie it is nice not to have the International Astronomical Union to worry about, otherwise Mustafar would have gotten plutoed.