DynamicViewDistance adjust the View Distance based on Target FPS and Max Foreground FPS to get more consistent FPS.
You can find those settings in: Menu -> System -> Advanced
The addon checks the FPS every second. If the FPS are lower than Target FPS the View Distance is reduced. If the FPS hit the Max Foreground FPS the View Distance is increased.
Additional to View Distance, the Texture Filtering and parts of Environment Detail (lodObjectCullSize) are also changed, which leads to a further performance boost.
Environment Detail could not set directly because of an annoying flickering effect.
The addon only affects Base Settings not Raid and Battleground.
I recommend a range of 20 FPS.
For my 144Hz monitor I use
Target FPS => 80
Max Foreground FPS => 100
For a 60 Hz monitor I would use
Target FPS => 60
Max Foreground FPS => 80
Be aware that Vertical Sync must be disabled in this scenario.