You can obtain the quality level locally like this:
local qualityLevel = UserSettings().GameSettings.SavedQualityLevel
Which returns an enumerator of this type:
http://wiki.roblox.com/index.php?title=API:Enum/QualityLevel
That being said, it is not recommended to make changes in your game depending on the quality level, because Roblox does not describe, nor guarantee, which tasks are performed for each specific quality level and which tasks are not. They may decide to reduce or increase the limits at which certain graphics tasks are performed at any time, or add or remove rendering tasks depending on the device, without any prior notice.
Secondly, you cannot find out the quality level if the user set it to “Automatic”. So another reason why changing things depending on quality level is not going to work out well.
As for sound volume, you can get it like this:
local volume = UserSettings().GameSettings.MasterVolume
Value between 0-1, it’s a float. Check if volume == 0 to see if the user has sound turned off.