I was using 90gsm in the R value comparison.

I tried a wind shirt in the past and it wasn't waterproof when I needed it to be, so I'll wear the lightest rain coat.

The montbell loses its loft when packed but within 15-30 minute of wearing is back to normal (and I suspect it's warmer than the alpha even when half-compressed). I usually only pack it tightly when I'm nowhere near cold weather anyway. My bag is empty enough that if I take it off to go inside somewhere I'll just stuff it in.