The reason why the VVT will feel like just a on or off situtation is because it is just that, either on or off, it has no inbetween.
So long as mamagement runs VVT then you can have it where you like.
Would be sheer stupidity not to have it, as the fuel savings are enormous on part throttle openings, as some RR operators do actually do experiments to satisfy their own curiosity about things and one has done a little research into this.
There was a recent article in PPC magazine about this very subject, not in depth but a good info bit under Walkers Workshop, and also a thread on here recently.
Any decent management if so equipped would be able to control this as all it needs is a feed for on or off.
tabetha