Replying to Layering up in hoodies

hey ns. Thinking about saga OG logo but wondering if it's gonna be warm for 15-30 degree weather(of course with a couple warm layers beneath it. And also if anybody has tried wearing a waterproof windbreaker underneath a jacket like the OG that isn't very waterproof or if the OG would hold up fine in rain. I heard it's a 5K waterproofing. Also wth does 2L and 3L mean on sagas anomie/fatigue. +k for something I didn't know or answering questions or in site on the matter