Here are some screenshots from my first tests to combine 3-pass xtrans demsaic and fast xtrans demosaic.
All have the same sharpening settings applied.
First shows 3-pass at left and fast at right. 3-pass has good details and background full of ugly artifacts, while fast has horrible details but a much nicer background.
Again left 3-pass, right is the combination of 3-pass and fast
For reference left the combination of 3-pass and fast with sharpening, right without sharpening