What kind of upgrade are you looking for? A mileage (+ co-pay) on paid tickets? Those require R class availability, so you want to look at that bucket.

R availability varies and it's a waiting game and a bit of a gamble as to whether you'll get upgraded. Just because it's 0 now doesn't mean there won't be upgrades available later. However, as a Silver, you would have lower priority, though you would be ahead of most if not all Silvers because you have a full-fare ticket.

P/PN do not have anything to do with upgrades (except for Global Services members, who can upgrade if the PN bucket is available).