H4 visa stamping for spouse who is working in canada

My spouse got her H1B visa stamped last week, currently in india. I am working in canada on work permit. I have valid B1/B2 visa. Can apply for H4 visa from Canada, if yes, is it going to be a dropbox / interview ? or Can I travel on B1/B2 and get converted to H4 after landing in USA.

Yes you can and most probably you may qualify for dropbox.

https://travel.state.gov/content/travel/en/News/visas-news/important-announcement-on-waivers-of-the-interview-requirement-for-certain-nonimmigrant-visas.html

Yes, you may travel on B2 and apply for a change of status in the US. It is highly recommended to apply for such a change of status after 90 days of entry on B2.