I did the China section of the Silk Road in 2019. Access to Xinjiang is unpredictable. When I was there I had a 24 hour secret police tailing. Car driving slowly behind me in the desert, in the distance. 24 hours a day. Crazy stuff.
The whole area south of Kashgar was off limits to foreigners. I got thrown on a truck by the police and driven past the section, which was a bummer because I really wanted to visit Yengisar. Your mileage may vary today, but it would be a shame to fly to Kashgar and then find out access is forbidden. Do your homework.
On the Pakistan side the ride ends in Islamabad. That's where Bin laden was hiding. If you are American maybe keep your head on a swivel.
The ride itself, I hear, is excellent and popular with local Chinese cyclists. You'll have no problem with it. Acclimatize slowly to avoid pulmonary edema.
If China is too much of a headache you could always go to Tajikistan and do the Pamirs there. You can ride on the border with Afghanistan and look across the river at it. Very exciting.