So, ladies and gentlemen...
Your attention is presented...
Well...
For a start that it is all about

This is a MiG-21, which was attached to the variable geometry wing. In theory, this should give it a multi-mode flight, the ability to adapt to different speeds and loads. In fact - I'm honestly not very confident that this will bring advantages in maneuvering and at low speeds, but the maximum speed will obviously increase

Now about what exactly will give an advantage:
- Internal volumes increased, allowing to cram more avionics and fuel
- Added two pylons for air-to-air missiles
- Wing got more advanced mechanization
- Landing characteristics [supposed to be] improved
- Better visibility

About gameplay features:
- Smooth change of speed, stability and maneuver during transformation
- The sound of the engine, as usual
- Towed decoy

Ah, controls. Well, controls are pretty standard, but:

1 - autopilot
5 - afterburners
7 - release/retract false target
8 - transformation

Okay. I finished.