I've only been following Vancouver for the last couple of months or so, but from what I have seen and reviewed they mainly play a 4-4-1-1, and it seems in the defensive phase like two flat lines of 4 defenders and 4 midfielders, with Reyna(SS/AMF) and Kamara(CF) helping out randomly, and the way Davies behaves in the defensive phase made me think he is primarily a SMF rather than a more attack focused WF with little defensive responsibilities..It could be that in PES terms Vancouver plays two formations during the match and morphs into a 4-2-4 kind of system on the counter/attack, so he could very well be a WF too.
I'll add WF, I don't know how to rank them as you listed, " LMF *, RMF (b), LWF (a), RWF (b)" I just enter the info in the editor for the website and it outputs the positions, I have no option to list them in a preferential hierarchy - I can only list "Both" for preferred side as an option. The WB position I will wait on, as I have yet to see Vancouver play that sort of system. I have seen him play LB before, last match vs Dallas, Levis was subbed off and he played there in the second half, his MLS All Star appearance was at LB, I'm pretty sure I've seen it at least one other time - and the commentators have made mention of him being able to fill in that spot.
I actually found him to be very responsible in his defensive duties, he helps his SB with opposition's wide players and I thought he was pretty frequently in that space around the upper corner of his own penalty area, his ball winning is composed and decent.
The BC and PC values I have not yet played one of the new PES games that have these, so I don't know how to rate them well - I know tomitos has made some posts regarding this but I have yet to go through them - If you or anyone else have values in mind for BC and PC for Davies or any other player that is missing them for MLS, just post them and I'll add them. Someone else with more knowledge can dispute or edit them later. I tried to make guesstimations from ladders for a few players and quickly stopped since I had no way to know ho accurate I was being not able to play with the values.
EDIT I tried to make him SMF, WF, SB . I removed SB, updated, added WF, updated, re-added SB, updated. And the PSD Editor still lists him SMF, SB, WF - lol can't be helped.