The dark spots on the floor looks like it's way too rich; does it smell like unburnt fuel when you're behind the car?
I'd say pull the plugs, see if they're dark brown or sooty. Pull the valve covers, look around at oil puddles, pushrods, any metal or coolant being present - expect to see some flakes from valvesprings. Might want to pull the oil filter, cut it open, pull out the media, and see what it's trapped. Expect a little debris on a new engine but shouldn't be much, certainly not a metalflake paste.
A little white smoke on startup isn't necessarily anything but condensation, if it dissipates rather quickly, as in light steam; if it's a cloud that hangs around, that could be coolant, and as AMX says, you'll likely smell it. If you see oil droplets in radiator & coolant droplets on dipstick, it could be from a number of significant things, and an unusually clean spark plug could pinpoint its location.