Hi,
The tail drive is dependant on where the drive is taken from. This is a matter for the main gear/ sprag bearing etc. You can get different gears for helis to make them a driven tail drive, or non driven (speaking from the main blades ). A non driven tail is not driven by the main blades during an engine failure (or practise auto) and while you have little/no rudder control to change where the nose is pointing, you have more energy at the bottom of an auto to make landing a little easier. On a 50 size heli you can auto with a driven tail, there is enough energy stored in the rotor system. On a 450 electric you have only about 25% of the energy you get in the 50 heli, so a non driven tail would be much better, then again, electrics seldom need to auto.

So, yes you can change a heli from one to the other, but you can't set one up for both.

With regard to dropping you head speed in normal mode and low collective, set up your engine idle for about 1/4 trim, before takeoff increase your trim to full. Now even when your throttle/collective is all the way back, you have some power to help keep head speed up.