I would never recommend that anyone do the 'on arrival' interview at YYZ unless you show up very early for your flight and are willing to endure the inane procedures that are enforced. When I was there a few weeks back, the lanes for 'interviews' were in 8 and 10 - except 8 was closed. 10 kept waving through previously-approved NEXUS passengers, on the basis that they had urgent flights to get to. Then 11 opened, but they would only wave through NEXUS passengers. My conclusion was that the folks running CBP at YYZ had zero idea as to how to optimize getting people through - they assumed that non-interviewees were more urgent. We finally got through (with 10 minutes to spare before our stated boarding time). The interview consisted of the agent giving me false information (that NEXUS included Global Entry and TSA PreCheck, but cheaper), and largely making other idle conversation until his computer finished processing our info.

My recommendation: don't bother at YYZ. Easily one of the worst experiences I have had with CBP, ever. If you live in the EWR / general NYC area, just schedule an appointment and do not deal with the unnecessary stress you will have to endure.