White suggests coolant but then the oil level is dropping, which is confusing.
Smoke on overrun can indicate turbo bearings and seals starting to fail. I suggest you check all levels repeatedly and thoroughly to look for changes.
Water can enter the oil system if the HG is failing. Clearly you don't want water going through the turbo, it's not especially good as a lubricant.
Before we get too carried away, it's worth considering the PCV (Crank ventilation valve).
If this is clogged or stuck you will get high pressures in the lower part of the engine which can force oil into places it should not be (such as the cooling system, which generally will be at higher pressure than the oil system when the engine is at running temperature).