Is drop box safe in my case?

Hi

I was on H1B Visa when my previous employer laid me off on 30th Nov 2016. My new employer has filed for H1 transfer through consular processing. I’m waiting to hear back from USCIS before 30th Jan, 2017. My questions are:

  1. If my i797 is approved, should I go in for drop box or is it better to schedule a visa appointment? I’m worried about my break in status (no pay stubs for December and January)

2.If I make a visa appointment, can I cancel it and go for drop box instead?

It would be great if you can answer one or both questions above.