Quote from https://www.scirra.com/manual/109/audio
"It is important to organize audio files appropriately, because audio files in the Sounds project folder are downloaded completely before playing, but files in the Music folder are streamed. This means if a Music track is accidentally put in the Sounds folder, it would have to download completely (which could take a couple of minutes) before it started playing. However, audio in the Music folder can start playing immediately since it is streamed from the server."
So the first thing to do is to make sure any Audio files you want to play immediately should go probably in the Sounds folder...
I would run a test first with just a few Audio files and place them in the sounds folder first then test it ...and then test against Audio files in the Music Folder
and see which works best
Obviously The sounds folder Files need to be Preloaded first using the method you mentioned
Hope that helps