21 days in Peru and La Paz. I have a 25L that I will definitely bring. Then deciding between my 30L North Face Duffle style pack or 50L Osprey backpack. My 25 L will be mostly tech and other items. Plan on doing lots of hiking including 5D Salkantay to Machu Pichu & Huayna Potosi in Bolivia. Will be taking mostly bus transport. So mainly just concerned if a 25L and 50L will be too much. I usually do the 25 and 30 for warmer destinations.