Find the balance
Try a jacket over the kind of layer you actually wear beneath it. Look at the sleeve length, shoulder room and how it closes when you move. A structured outer layer and a soft overshirt create different outlines even when the colour is similar.
Read the garment, not just the label
Check the composition, garment measurements and care instructions for the particular piece. Similar names can describe different cuts across collections. Measure a garment you enjoy wearing laid flat, then compare the chest, length, waist or inseam as appropriate. Keep any care treatment consistent with the label.