As a cyclist who commutes along Smithe requently, I think a Smithe street bike lane is a terrible idea. Right now, the access that is provided to Beatty street is great and worthwhile. However, continuing up Smithe street is a waste of time for most cyclists. In order to hit all of the lights (even with a separated bike lane) one would have to average over 38km/h and put out over 400 watts for about a minute. And make the light coming off of the Cambie bridge. That is tough for most cyclists, let along commuters with a backpack or panniers (in all my attempts I've made it once).
Strava: Smithe Street Lights
Adding lane separation, and potentially restricting right turns would jam up Smithe onto the Cambie street bridge in the morning rush. It would only provide access to another good bike route all the way up at Hornby as in order to get onto Richards you'd have to cross three lanes of traffic to make a left turn. Directing bike traffic to Robson street where traffic is slower and the road is narrower is a much better idea. After the climb up Beatty (which has a bike lane), Robson has less of a grade and it is easier to make a turn to get onto Richards.
As for Nelson? I very rarely bike it, but drive it almost daily. It is a zoo with traffic. There are frequent right turns at Howe, Richards, Mainland and Cambie. A lot of those are cabs zipping across two lanes to make the turn into Yaletown. Why choose Nelson over Helmcken, which already has the Comox bikeway connection? I find this choice a little dumb as well. Obviously the south connection to get onto the Cambie bridge from Helmcken would require more work than from Nelson, but I think there is plenty of room along Cambie to make the connection from Helmcken park to Nelson (as there is a landscaped median in the middle of the road).
Changes to Smithe/Nelson, whether or not they eliminate a lane of traffic (god help us if they do) will slow the flow of traffic and cause further backups on those two arterials due to conflicts with turning cars and bikes in curb lanes. I am ALL for improvements to bike infrastructure (the Richards bike lane separated by parked cars is great) but I would definitely advise against either of these two routes unless cyclists are comfortable in traffic and can move very quickly.