Also sounds like the glow plugs are bad. White on cold start is normally unburned fuel. Rough idle on cold start is normally one or more bad glow plugs. Does it sound/run better once it has warmed up? It should.
Does the white smoke evaporate quickly once it is expelled? What does the smoke smell like? Does the water tank pressurize quickly at startup, or does it bubble? If it has any hint of anitfreezed smell out the exahust or the cooling system quickly pressurizes upon startup, then it is highly likely the head gasket is bad, and this would account for the lack of power. My 1.5 caddy did this some and it didn't have much power either. I found that several head bolts were loose. Some who repair vws, don't follow the protocol of retightening the head 10 min. after warmup, then again @ 1000 miles. I don't think the mechanic that repaired my 1.5 with the previous owner followed this protocol since the head bolts were loose. You could check the head bolts for torque to see if any are loose, and this would help to narrow down your problem.
...BTW your Bieber avatar is awesome.-Malone