You can mix using both the app and the website as long as you are careful not to change the same inspection in both places at the same time.
If you edit on the app, make sure your changes are synced - ‘Upload required’ should be 0. If your phone is online, this should be pretty much immediate.
If you edit on the website, the app has to download those changes. It does this on startup, fairly regularly whilst in use, and if you pull down on the Inspections table to do a manual refresh.
If you do make a change whilst there is an outstanding change somewhere else, whichever change makes it to the database last will overwrite the other change.