Of course I would not even consider trading row 6 for row 1, so my question is, if I waitlist and clear, will I lose my row 6 seat before finding out if I'm being offered row 1 (which I would refuse) or row 2 (which I would accept)?
Yes. As soon as you clear, your seat assignment in Economy will be cleared and you will get a seat assignment in First.
Now, if United Easy Update works and notifies you in a way you can immediately know, then you can check to see what seat in First you were assigned and if you can move to something better. If you can't, chances are 6F will still be available.
However, Row 1 on the Airbus is not bad, frankly. You can't stretch out as much as Row 6, but you don't need to keep your knees bent 90° and your feet flat to the floor, either.
