B fare clears into PN for any elite. I'm not aware of any situation where F>0 and PN=0, hence as long as there is an F seat available any elite on a B fare would clear up on the spot into PN (or call in to have it processed if the website is being difficult). Note that for CPU-eligible flights B fares are not clearing into the same bucket as GPU/RPU/CPU's which clear into R, they are clearing into PN.

Additionally as noted by the OP's quote from the website any B fare that doesn't clear instantly comes before GPU/RPU/Miles+CoPay at each of the confirmation windows and the website goes on to say:

At 24 hours from departure, waitlists will expire and automatic processing of upgrades, per the priority listed above, will continue.

So therefore B should continue to have priority on the waitlist over GPU/RPU/Miles+CoPay in the event an F seat comes open at the last minute.

In terms of GPU on W vs. miles + money on B, it would depend on status but the great unknown in this equation is R availability. If the GPU has EF and finds out R has come open before united.com does a sweep, they can of course call in, jump the waitlist, and confirm into R on the spot.