On the 225 we fly 3-cue (4 axis) and set the IAS datum to Vne - 10kts. The autopilot prioritises vertical modes (ie ALT or VS) when above Vy so it holds the height and accepts it can't do 165kts in level flight. In fact it sets torque to around 2% below MCP to give some buffer against exceeding MCP. In strong turbulence, its sometimes necessary to fly 3 axis (2 cue) and manually set the collective below MCP to avoid frequent exceedances of MCP (which apart from anything else triggers a loud gong).
We set the IAS datum to Vne - 10 so that it will accelerate during descent but not get too close to Vne in turbulence. It does sometimes get to 165 at which point it would start to back the power off.
For the 225, surprisingly it gives best range at only slightly below flat out - reducing speed by around 5kts to cruise at typically 145 kts gives best range, any slower and range gets worse even in still wind. If we do this (not often, as you are not often short of fuel in a 225!), as 212 says its best not to cruise in 3 cue to avoid collective hunting.
HC