What is the recommended way to export a file with burnt in subtitles

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I have a DCP where there is an OV with not subtitles and a VF with subtitles in it. I want to export it to a mp4 file that is going to contain the subtitles. What is the best way to do this?

First, what controls if the subtitles are visible in the preview or not? I am on development version (2.13.64), so that might be the issue, but when I open the VF, it does not display the subtitles (the standalone player can play them). When I add a subtitle file (xml, hte one that is in the VF) to a OV I opened, it shows them in the preview but stops showing them when I move them to start of another reel.

And what options should I select to burn the subtitles into the exported movie? "Burn subtitles into image"? Is it neccesarry? Would just exporting the VF with the subtitles work as well?