Arms out wide like a T to fire the mid back.
Pinch your shoulder blades together at the top, keep your neck long and relaxed.
Arms out at shoulder height with thumbs up puts the mid back, especially the muscles between the shoulder blades, in charge of lifting the arms against gravity through horizontal abduction. The rear shoulders assist on every rep, and the pause at the top turns the squeeze into real time under tension. It belongs in warm-ups before pressing or rowing days, or as light volume for anyone whose pulling has gone quiet through the mid back.
Both, they hit different jobs. T's train lifting the arms out wide from the mid back, W's train pulling the shoulder blades down and together with bent elbows, so they pair well in the same warm-up.
Your upper traps are hijacking the lift. Set your shoulder blades down before the arms rise and use less height if you have to, a lower lift from the right muscles wins.
Before upper body sessions as activation, or at the end as easy extra mid back volume. They cost almost nothing to recover from, so frequency is your friend.
