Robabanban Measure the dimensions of the battery compartment in the car. Any 2S lipo battery with a JST plug (smaller red plug) that can fit in the compartment can be used. A battery with a higher C rating should give more power, so a 40C should give a little more power than a 20C, as well as a larger 20C (e.g. 1000mAh) will give more power than a smaller 20C battery (like the stock 700mAh), while also giving longer run times.

Robabanban It is very similar but there are some significant differences, in wing design in particular. The Radjet has little pods at the tips. This Dragon Jet has small winglets that sweep up slightly at the back. So if I had to guess, I would say the Radjet will be faster and this Dragon Jet will be more stable.

Robabanban If you get really creative and cut up some foam, you could probably use an EDF, but it is designed specifically for a brushless outrunner.

Robabanban This is RTF, meaning it comes with the transmitter. It is a simple 2 channel design, with throttle controlling flying height and thrust differential controlling left and right direction. It is basically a copy of an old Air Hogs toy plane from many years ago, Mini Storm Launcher.