H1B stamping dropbox experience in Canada

Hello all,
I plan to get my first H1B visa stamped in Canada. I think I’m eligible for dropbox as I meet all conditions for it. I had a previous F1 visa that got expired in 2020. I’m also a PR of Canada. Has anyone got their H1B visa stamped successfully through dropbox in Canada whose previous visa expired in 2020 timeframe?
Also if for some reason the stamping gets refused and the consulate asks to come for interview, do they provide a interview date close to the refusal date or we have to wait like everyone for an interview slot?
Any info would be greatly appreciated.