Excellent choice — #5 of 31 Wool ranks #5 of 31 fabrics for warmth without weight. It is one of the best fabrics for this. Ranked on warmth relative to weight, with a packability bonus. The top pick is Cashmere.
Wool measures 55/100 for breathability, 15% moisture regain, 85/100 warmth, at 280 gsm. Warmth-to-weight is the metric: 85/100 warmth at 280 gsm is an excellent ratio for packable insulation.