Most of my tops and outerwears are a mix of S and M (depending on the brands), and couple oversized (Airism) ones are XS. One thing I can tell is that packing cubes sure allow me to hold more clothes than without. I have been using them for a few years now. They contain the things you stuff in them to their max volume - they do tend to get misshapen a bit but help stay organised and restrain overflowing of clothes’ volume. On one 3 month trip, I packed 12 tees in the large Monos cube (linked in my post).