Questions about the default values for some subtitle and audio settings

[raziel711]

I've seen that demuxer-mkv-subtitle-preroll=yes seems to be used fairly often instead of the default value, index. If I'm reading the manual entry correctly, it could potentially be better to use yes instead of index for older mkv files. Are there any other specific cases when it would be better to use yes instead of index?

Secondly, mpv's audio resampler uses audio-resample-filter-size=16 and audio-resample-linear=no by default. However, ffmpeg's SW resampler uses a value of 32 for the filter size and yes for linear interpolation by default. Is there a reason why mpv's audio resampler settings do not use the same defaults as ffmpeg, and if I were to manually set them to match, would it actually have any noticeable improvement in audio quality?

Lastly, is there an equivalent to profile=high-quality for audio settings? I've tried using audio-swresample-o=resampler=soxr in the past, but that usually results in occasional frame drops.