No one can see or access your snippets or mashed videos unless you share them. If you don't upload your videos to a social network, cloud service, or email them to someone else, they're only stored locally in your device within the 1SE album in your Photos app.
Where do the videos in your Instagram account come from?
The videos we showcase on our Instagram account are the ones our users post using the #1SEme tag. These are only visible to us if our users have a public Instagram account.
So, don't worry! Nothing will be shared or seen by others unless you want to.