The only format we recommend using is MP3. MP3 by default -when you're downloading or rendering- has good file sizes and audio quality for listening. Almost every audio file you come across the internet or device is typically in an MP3 format, even in videos.
Bitrate is similar to the data rate in videos. It is how much data is being stored for the audio every second it is recording. Most audio files and videos have an audio bitrate of 90-130kpbs, this size is perfectly fine for listening.
The sample rate is the quality of the audio is played at, similar to the data rate for videos. It is recommended to keep it at around 48kHz or higher, depending on if you have professionally recorded the audio or if it is just a general audio file. Don't set it too high as it won't affect the audio file.
This affects how many speakers or audio outputs the audio will be played on. These days the default is 2 (Stereo) and works for everything. If you are to use Mono, ensure that you only have 1 speaker/audio device output, but we still recommend keeping this to 2.
Typically audio files aren't very large in file size, depending on its length. But we don't recommend increasing the file sizes by altering the rendering/recording settings over the amount needed. Doing this will not magically increase the quality of the audio and will just result in unneeded large file size.
While this isn't necessarily an important subject, in order to keep an efficient workflow going and ensuring you know what each file is, we recommend a structured naming convention. This will help you to recognize the files and where they belong when you are searching for them in your library or computer. Giving your files a randomly generated name can really slow down your work time.