I haven't flown China Southern longhaul, but I've had good experiences with their internal flights in business class or FC (which seem the same to me, although the prices can differ slightly). IME they fly nice modern planes in good condition, I think mainly 737-800s.

On PVG-CAN, my impressions is that there can be advance schedule changes and cancellations; my travel agent was contacted and then it was no problem changing to another flight on the same day. Some English is spoken, they seem to take special care of (surprisingly rare) foreigners (walking me to security and the lounge, attention from the purser on board), and nice slippers were given out on board, where only liquids (including beer and rather bad wine) were served--no meal on my flights of an hour or two. Their lounges are nothing special, with water/tea/coffee and not much else (Chinese newspapers), but lots of smokers. The routine seems to be that you stay in the lounge while coach boards and sometimes they drive you to the jetway or plane on the tarmac, although in PVG I walked along the regular concourse to the plane, they closed the door and departed. CZ is the only mainland Chinese airline that I will fly willingly. PVG is a nice modern airport that appears to be underutilized, so that either connecting through PVG or HKG should be pretty good. However, be sure that you don't have to change airports in Shanghai.

If you're not trying to stay on SkyTeam, Cathay through HKG is wonderful in business class, including their lounge in HKG. Can you do SQ through SIN or is this too far to get to CAN? Is there a good connection at NRT, perhaps on JAL but ideally in the same terminal?