Hey @oz43.
When I learnt I used my 10m from about 10-15 knots. Then used my 8m for 15-20 knots. But my Neo's have crazy bottom end so you might want to shift those up by 2 knots.
Now I'd use a 12m in the lower wind range and then probably change straight to my 8m. But I have little interest in going fast and I much prefer to work the kite off the foil and do lots of loops in turns etc to keep foiling.
What I'm finding more and more, as I test different foils and kites, is that the type of foil (and kite to a lesser degree) has a big impact on how easy it is to learn but also how much power you want from your kite.
What foil/board are you riding?
I feel I learnt a lot in my early sessions riding in lighter winds and having to work the kite a lot. It makes you really think about how power from the kite transfers to the foil and how the foil generates and loses lift but it's easier when you are on a freeride style foil that produces lift gradually rather than the more sudden lift produces by more advanced foils. There is some much development in the foil designs at the moment that is becoming far far easier to learn with less power.
Having said all this, once I had the basics, some of my quickest progressions has been on a 5m kite in strong winds.
Overall it's all just a lot of fun and so many new things to learn