This is very interesting topic!

You introduced an interesting idea of VO.

My understanding is
at any speed, the ideal CVT transmission can
make engine run at rpm that generates PEAK power

But there is a threshold speed, below this speed,
if the CVT transmission keep the engine run at peak
power, the drive force on wheel exceeds the taction
limit between wheel and ground, causing slippery.

And you call this speed as VO

Now talking about best performance.
At speed above VO, the slippery does not happen, we can simply adjust CVT to make engine run at peak power

At speed below VO, My think is,
as long as we can apply the drive force on wheel that is almost going to cause slippery, we reached the best
performance. We call this exact force on wheel as FO

So all configurations below give best performance
since it applys FO to wheel

Your way of run engine at RO with slippery clutch

Make the engine run at the rpm that provide
power = FO*speed, and make CVS gear ratio fit
to translate this RPM to the vehicle speed.
i.e. Gear Ratio = RPM of Wheel/RPM of engine

You way is more practical and doable in reality.

My way is only doable in theoritical sense, not in reality. But I guess my way at least can avoid
the damage on clutch. :)