Question about MUA waitlists.

Is there any way to see the waitlist before buying or is expert mode with the fare buckets the best clue to real availability? Also wondering how MUA's are prioritized vs plus points. I'm a lowly silver (and explorer cardholder) so basically everyone is above me but wasn't sure if there is an MUA vs. plus points chart somewhere. Also, I've read that those who buy PE with MUA to Business prioritized over those who buy E with MUA to business - is this correct?

If its helpful to know, I'm inclined to buy PE and MUA to Polaris but everything I've seen says waitlist. I've never used an MUA so if anyone has tips, I'm open to them as I'm considering it for an international trip.