“VW's new system behaves as Fiats - to avoid patent infringement while still exploiting a Miller/Atkinson cycle?”
If you mean this VVA of VW:
it is a simple two step VVA.
Honda’s V-TEC does (or can do) the same and is some 30 years older.
The V-TEC drives each valve either by a wild cam lobe, or by a mild cam lobe, with the selection based on hydraulically displaced locking pins (as VW’s VVA) .
In some of their models, the VW-group uses the above VVA to deactivate the valves of some cylinders, in some other models VW uses it to run the engine in one of two different modes (typically: sport mode and economy mode).
The MultiAir / TwinAir of FIAT, Alfa Romeo, Chrysler is a way more sophisticated (and at the same time “mechanically” simpler) VVA (Variable Valve Actuation system) wherein there are available infinite valve lift profiles (continuously variable, from full deactivation of some valves, to full lift - full duration).
The hydraulic MultiAir / TwinAir system of FIAT has true electronic control, based among others, and on the feed back from the exhaust; it needs neither a throttle valve nor VVT (Variable Valve Timing):
The PatAir (the outgoing air control):
adds an infinity of additional (and more efficient) modes of operation (unlimited Atkinson Miller cycle) to the MultiAir / TwinAir of FIAT.
You also write:
"Why does it take 1000hp to displace the air at 400km/h then?"
The 400Km/h is anything but a small speed: it is the 1/3 of the sound velocity in the air; and the frontal area of the Veiron is about two square meters.