Vmax is the maximum speed which can be achieved in level flight at maximum engine (probably max continuous) power ie where your power required curve crosses the power avaliable line. Unfortunately the term is often used in the military when talking about a flight envelope limit.
For example the Sea King has a FE limit of about 127 kts but the Vd (design limit is 157 kts) the Vne is apparently calculated by reducing the Vd by a safety factor of 1.1 bringing you into the low 140's. The British Military Release to Service then reduces that further by another safety factor to get to 127 kts. Generally speaking, the power at the FE limit is about 65% matched Tq and is nowhere near max power available.
As for the Lynx - it's Vd must be around 212 kts since that is what Westlands managed in the record. Apparently it only starts to get interesting in handling terms above 180 kts. I have had one (Mk 7 no TOW) at 165 S&L, smooth as silk with loads of power left.
The answer to the original question is that for many years only symmetrical aerofoil sections were used on helicopters but now improvements in blade construction allow several different sections to be used in one blade. The problems are all to do with pitching moments on a cambered blade as the AoA changes producing instability and vibration and therefore undesireable control loads.
Prouty's favourite saying regarding blade design is 'what you gain in the hover you lose in forward flight and what you gain in forward flight you lose in the hover'. Designing one blade that performs perfectly in both flight regimes still seems to be the holy grail of the helicopter designer.