Service Canada:
Two desks - one person was chatting on the phone, the other couldn't see me initially but came forward to help when she did. Told her I'm a new immigrant and ... "oh! you're here to apply for the SIN. Please come."
She asked for my number and address - dint want the intl number and the address I gave was of the airbnb I'm staying. She said we will never call that number or send anything to the address so no need to worry or update it later. It's not reqd.
Entire process took 5 mins. Got a printout and walked to collect my bags.
P.S. There's only a few restrooms between arrival gates and immigration and customs AFAIK. You might want to get it done when you can in case immigration/customs takes time.
Customs:
This was the most time consuming process.
You'll be guided to a huge hall with about 6-7 counters. It was mostly empty with 2-3 people being served. I was called up - the officer took my landing card, passport and entered some info in their system.
I had already made a "goods with me" and "goods to follow" list in detail with all fields filled up and value mentioned. I carried two copies of this set.
Handed them over - the officer went over it carefully and added the individual values up. I'd not mentioned the address on the form so he asked me to write it down. I asked him if I could give the temp airbnb address (I don't rem his exact response) but I ended up giving the same one as the PR card delivery address.
He went into a room, came out with a CBSA printed form with the Total value of all goods I'd mentioned and stamped & signed over all the documents. Asked me to sign too AFAIR. He mentioned that if I'm having these items shipped I'll have to hand this to the moving company so that I'm not charged any import duty for bringing these items over (which were in the list).
No questions were asked about the items or their value. He did not even ask me to open any of my bags.
Though I did see some people being asked to open their bags. Maybe having a detailed list with all values helps. Maybe, Can't say for sure though.
Exchanged pleasantries and he guided me to the exit.
There's a restroom, a Tim Hortons counter and some small places to eat right before the exit door. You might want to give them a try if you feel like.
Took a taxi from the rank and came to the airbnb. The taxi fare was $45+tip (AEROPORT TAXI AND LIMO) flat rate. The car was big enough for a few more people and some more bags. Uber estimates were higher and I had some heavy bags.