OK,
Here is a bit of theory.
Wing twist - twisting the wing gives different angle of attack in different sections of the wing.
Why wing twist is required? Airflow has a tendency to change direction toward the end of the wing on the bottom of the wing and toward fuselage on the top of the wing. Thus real angle of attack is actually higher at the end of the wing if wing has no twist.
This movement also results in induction drug at the end of the wing, which is very high compared to the full drug of the aircraft.
The ways of reducing induction drug is making a very long wing (which is not always feasible) or have winglets installed at the end of the wing tip.As for forward swept wing - it has high positive twisting load as result of the lift force.
Normal swept wing self compensate for the wing twist. When load increases wing bends and twists as result. This movement decreases the angle of attack at the end of the wing. On forward swept wing it is quite opposite. That is why it requires totally different wing structure under the skin. The whole airflow focus of the wing is different and requires a special attention to control it.
The whole concept makes aircraft very unstable and responsive to the control input altogether. Sometimes more responsive than experienced pilot could handle.
Fly-by-wire system is only one way to control the aircraft and has nothing to do with aerodynamics at all as well as thrust vectoring. Thrust vectoring is not used on SU-47.
If you look closely at the Su-47 in flight - you will notice that control surfaces in some situations are in awkward position to the given situation. For example you may see Su-47 about to touch down and main stabilizer and front canards are in a nose down position.
This is due to the rear moved CG and whole focus of the flight surfaces moved backwards.
The same goes for Su-35. Example:
http://www.flymig.com/maks_2003/images/su-35.landing.htm
That is the main difference between Su family aircraft and many other similar Western fighters. All late Su family aircraft have CG moved further to the back which makes aircraft extremely unstable and at the same time extremely maneuverable to the point when designers had to employ fly-by-wire system to control aircraft.
You will also see examples of controlling aircraft to the point of extreme maneuverability in Su-26, Yak-50 and Yak-55 aerobatic aircraft. Those planes could perform "Abracadabra" (when aircraft literally flies backwards) because CG is moved slightly further back and masses distributed appropriately to gain enough momentum to start what looks like uncontrollable spin that results in reverse flight direction.
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