dvd burn

When did you get this error message? When you tried to open the app or when you tried to access files to use in the project or when you tired to burn?

Go into System/Security & Privacy/Privacy/Full Disk Access and add Burn to it. Also make sure it's listed in the Files and Folders section.

Best is a relative term. There's a free app, Burn, that works well but has limited menu design features. But it seems to work pretty good.

Go to the App Store and search for "video DVD" and you'll get a lot of potential candidates. Many have demo versions you can try before purchasing.