In the tests I've been doing, the order seems somewhat crucial. If I list a 5000 kbps file after a 2500 kbps file, it never played in my tests. Whereas if I list the 5000 first, it will play (given sufficient bandwidth). I don't know why but this is what I found, so now I list the higher bitrates first.
If I list the same mp4 file with both 'SD' and 'HD' designations, it seems like often (but not always?! maybe depends on the roku model?) only the first instance will be chosen. SD-configured devices may not be able to play the title if HD is listed first, whereas if SD is listed first, the 'HD' branding logo does not ever appear. The former is a real problem!
Perhaps you'll say there's no reason to ever list the same file as both 'HD' and 'SD' but our goal is to have the 'HD' branding logo display where appropriate (2500 kbps file encoded from HD source). This may lead to a whole nuther discussion about how our content is not true HD and shouldn't be branded as such. What we've found is that a 720 wide mp4 encoded at 2500kbps looks fabulous and incredible on a 4K (as well as every other) TV and we don't see the point in spending more resources to produce, store and distribute a larger file which looks marginally better if any difference is noticeable at all.
aspiring