The answer is YES, ABSOLUTELY. Indeed, we don't ask you to login with your Instagram or Snapchat account on Fastory and we don't publish anything for you.
Once your Microsite or Video Story Ads is published on Fastory, we automatically generate files in phase with the channels constraints (regarding resolution, type of files, interactions allowed, etc.)
For Video Story Ads, you will receive an email with files (one for each screen). You'll have to download and then upload them on the app with your mobile.
You can also send the assets directly on Facebook, Instagram Ads Manager and Snapchat advertising tool .