Any creations, edits, or deletions to a file or folder will trigger updates in Merge. Some exceptions are due to the limitations of third-party platforms:
Box — updates will not be instantaneous. This is because they do not allow developers to create webhooks in the root “All Files” folder, so we cannot capture real-time changes if someone adds/changes/deletes a new folder or file in the root “All Files” folder. However, it will be captured during periodic syncs.
Dropbox — updates will not be instantaneous. We do not yet have webhook receiver support here yet, so changes will be captured during periodic syncs. Deleted files/folders will be detected via deletion detection feature which runs every other day.
OneDrive/SharePoint/Google Drive likes to batch their updates every ~1-2 minutes, so they may not emit a webhook receiver payload instantaneously after the user makes a change.
The content type won't affect whether or not you receive an update.