if the video quality rule configurable?

There are 4 video quality as : “low bandwidth”, “low definition”, “standard definition”, “high definition”;
the default video quality is “high definition”, how to set the default quality to “standard definition”?

Another qustion is that:can I take out the “low definition” and “high defintion” option? When the bindwith Change, the video quality only fluctuate within “low bandwidth” and “high definition”.

Interesting question.
With many participants it seems to be always advised to lower this setting. Any way to change the standard quality to a lower setting?