a) Right now, because of extensive labour shortages, plan to arrive at YVR 3hrs from departure. During that time of day there will usually huge lines everywhere.
b)The luggage experience at YVR is quite good. Most of the time they aren't strict with carry on luggage and even if they do bug you some polite negotiating will do the trick.
c) TSA precheck doesn't have its own line but you can use the Nexus line, just ask the worker there.
d) Don't even bother with the Plaza Lounge, the Starbucks is many times cleaner and nicer. The AC lounge can honestly be decent but is usually packed to the brim.
e) The WS inflight experience is definitely laid back, but nothing special. The planes aren't crazy new and many do not have ANY inflight entertainment. Some of the flight attendants are very very nice and really make you believe the Canadian stereotype, but others can be plain rude. YVR however is a very nice airport and really chill.
Hope you have a good time in Vancouver, it really is a beautiful city to fly over.