Questions about traveling to Kyrgyzstan, Tajikistan, Kazakhstan, or Uzbekistan

I want to take a ~3 week vacation to either Kyrgyzstan, Tajikistan, Kazakhstan, or Uzbekistan. I really like hiking and landscapes. I know 3 weeks isn't enough time for all 4 countries, so I am trying to pick 2 or 3 of them. My initial thought was probably Kyrgyzstan and Tajikistan because it looks like those are more nature focused. I'm not sure if it would then be possible to squeeze in Uzbekistan for the culture. Can anyone give me suggestions on which countries? And also things not to miss out on. Thanks!