White smoke can be perfectly normally in cooler climates and just after starting the motor. If you have white smoke after driving for 15 min. that can be a sign of coolant leaking inside the motor and coming out the tailpipe. So, the timing of the smoke is a key clue.
Adding oil between oil changes isn’t unusual. That’s why you are supposed to check your oil level when you fill up with gas. A quart in 500 miles is excessive oil use. A quart every 3,000 is just fine.