@"Pallas"#p18202 That's a good video and exercise.
To clarify, my question is less about playing hands together at different volume, but more about how to play chords very softly staccato. The shorter the staccato, the harder I find to keep that chord soft without having ghost notes. Although in my example the chords are in the left hand, if I switch the score and put the staccato chord in my right hand, I'd still be having the same problem. Whichever other hand playing the single notes melody, I am not having too much difficulty controlling its volume to make the contrast I want. But if my left hand staccato chord can only go down to piano, then my right hand have to play at mezzo-piano or louder to stay above. In that case, the contrast would be okay, but the entire dynamics are shifted higher than the score indicated.
