In my first years i also could rig my 12M chrono on 30m lines and cruise strapless around on a summer breeze with very little margin for error. Was really enyoing the silence and sensation of foiling with the smallest size possible.
Eventually the hunger for more speed and power grew, started racing, put on straps and kept shortening the lines every few months until i discovered the possibility to boost really big in mediocre winds. In fact, i boost bigger on the foil in 18kn of wind on a 11m than a full on storm session with the twintip.
The windrange on a hydrofoil of a kite depends more on your riding style than on any other board. A 9m foilkite on a hydrofoil can be used roughly from 8-25kn, depending on your line length, from cruising to racing, boosting and everyting in between. Neither one end of this spectrum is wrong, just different. If you are on one extreme end It is hard to understand the other extreme (under- vs overpowerd).