My guess is that an independent Tibet would have developed at about the same pace as neighboring Bhutan, which abolished slavery in 1958 and turned into a constitutional monarchy in 2005.
There are still human rights issues in Bhutan, but it's a far cry from where they were 70 years ago.
Okay. Is there some comparison of living conditions between modern day Bhutan and Tibet?
I guess such comparisons are hard to make and bound to be subjective.
According to [1] Bhutan's HDI was 6.17 in 2018, while according to [2] the regional HDI of Tibet was 5.85. So at the very least they're not particularly far apart from each other.
[1] http://hdr.undp.org/en/countries/profiles/BTN
[2] https://en.wikipedia.org/wiki/List_of_administrative_divisio...
Also, "figures show that since the early 1960s, the Tibetan population has been increasing, probably for the first time for centuries" (https://en.wikipedia.org/wiki/Human_rights_in_Tibet).