Some of that difference makes narrative sense.
Like the discussions we had earlier about the ships, the droids in the PT era are top of the range and brand new.
I type this on a PowerBook G4 which in it's day was the Rolls Royce of laptops (the first widescreen 17" screen laptop etc etc).
The square bracket key no longer functions, the DVD 'orifice' has a snap in it, the screen is fading to pink, I have to plug in a cooler fan because using flash heats the aluminum casing to the point that it irons my legs.
In TPM Artoo is the brand new repairbot on a Royal Yacht.
In ANH he is the beat up ancient repairbot on a consular ship owned by a Princess so he has gone down a notch but he still a well constructed piece of kit used by the upper classes.
The other droids in the Jawa Crawler are a mixture of beat up/patched up industrial equipment and "unique fixer upper opportunities".
You should be careful to pick away what doesn't work because it's just being fancy for it's own sake or just being there to make George's kids laugh and what doesn't look like Star Wars 1977 because the object isn't old and broken yet.
The jets are narratively functional.
A car needs wheels.
A spaceship repair droid probably needs some kind of independent propulsion (to do it's job).
In a film a character may use a cars wheels to do things beyond it's design specifications (like kill the bad guy).
In a Star Wars film a droid may use jets designed to maneuver in space to make short hops into the air (flying like Superman is probably a step too far).