Specifically what is the list of all setting changes from last versions defaults?
They covered it fairly well in the build notes:
3. Changed: Switched back to old Core Audio hardware buffer size presets (Hardware Default, Maximum, Maximum Power of 2). The default is now Hardware Default as it was prior to 6/29/2015.
4. Changed: Added larger software buffering sizes (750, 1000 ms).
It was really only one setting
default change. I don't think the change will apply to you at all if you have a previous build installed (it should only apply to
new installs with this version or newer). But, to explain, the change was that for the past few versions of MC20 and MC21 (those released since 6/29/2015) for:
Tools > Options > Audio > Audio Device > Device Settings > Buffering > Hardware was
Maximum.
The default for that setting is now
Hardware Default, as it was for all previous versions of MC. This was changed in June in an attempt to help users with drop-out issues. It generally didn't work, and created a bunch of
new issues for other users (with more typical hardware). So, they put it back. If you suddenly start to have issues with audio playback in the newer builds, then check this setting (and try Maximum if Hardware Default isn't working right).
They also
added, at my request, two additional (larger) options for
Tools > Options > Audio > Audio Device > Device Settings > Buffering > Software (750ms and 1s) which were previously not available. The default setting for this option, however, did not change.