Question about optical flow in Adobe

Quick question about using optical flow to smooth up slowed down footage. I select optical flow on the clips I’ve slowed down in my project, but do I also have to choose optical flow in the time interpolation field when I’m exporting the video?

To complicate it further, I’m looking to export a DNxHD “master” file, then convert that to H.264 for uploading to youtube. So how do I ensure the optical flow smoothing survives to the H.264 file for youtube?

Note: my video is 2 minutes long, so uploading the DNxHD file directly to youtube may be an option, I don’t mind a long upload time.

I’m following this tutorial to ensure my video looks good on youtube.