xQuant will be multiplied with your devicePixelRatio. Hint: If you are using a 2dpr device you can set 0.5 to simulate 1dpr device.
greed is multiplied with the useless extra pixels of a source candidate and "added" to the next lowres candidate.
tLow and tHigh are working together: tHigh is a threshold (tLow not, it is a resolution booster), if the useless extra pixels do exceed the tHigh threshold the tLow res booster will be added to the resolution of the lower res candidate.
Wether viewport should be changed while dragging (input/checked) or on drag release (change/unchecked).