Do you prefer to push with the bow arm or not?
NO! The bow arm (I think) should be set and essentially static. When you talk about expansion, that is a motion produced by the string side shoulder that results in pressing the bow shoulder/arm out towards the target. BUT absolutely NOT any muscle or bone movement on the bow side.
Expansion (for me) is the feeling of pressing my sternum (chest) out a little by ONLY pulling the string shoulder back and NOT the bow shoulder/arm. That action will press the bow side out without any further bow side muscle activation.
Arne