This is a one at a time operation. Should only take a few seconds per master. This is definitely creating new media. And this shall create new timelines.
You could do like Tim suggested and do this a little bit more like a comp instead of timeline by making this all a comp I’m Batch. But my recommendation at this time based on what I think your experience might be is just to do it one at a time using the convert rate button in utilities. Step one, make sure you understand how to achieve it in flame and it passes QC. Then perhaps at a later time, step two, optimize how you do it.
Helpful?