A very simple and straight-forward app to use to record audio.
I tested on some web conference presentations and it worked well, including auto stopping within about 10 seconds of silence at the end of conferences. (tested on Yosemite 10.10.5)
Re the settings, my ears found that aac sounded slightly better than mp3 (for equivalent bit rate). And that the conferences I recorded sounded slightly better at 128 kbs than 64 kbs (which had a bit of tinny sound). Though this will vary depending on what quality the web conference, or other source you use, is 'broadcasting'.
(Following the rule that, recording at a higher bitrate than what is broadcast or played back as, does NOT result in better audio.)
Note to MU staff: The current Piezo version is 1.5.9 (not 1.5.8). 1.5.9 was released Apr 17 2018.
Ref: <https://rogueamoeba.com/piezo/releasenotes.php>.