During analysis of TableView performance with the SW pipeline I noticed that a lot of fillRect calls are made with Color.TRANSPARENT while compositeMode is SRC_OVER.
Eliminating those redundant calls gives the benchmark a performance boost of ~20% on low end Windows machines.
Note that NGRegion rather confusingly uses both javafx.scene.paint and com.sun.prism.paint. Color.TRANSPARENT referred above is from the latter package.
It might be more universal to implement that optimization in PiscesRenderer (which already optimizes fully opaque colors) though this approach may have higher overhead at such low level.