Maps of the Silk Road differ and are often approximate if not inaccurate. Nor is there one Silk Road. I’ll take this one, which appears to be in the public domain, as a simple reference. It shows the main route from Chang’an, now Xi’an, in Shaanxi province, going north and south of the Taklamakan desert or Tarim Basin. The westernmost city in modern China here is Kashgar or Kashi. From there the road passes through Tajikistan (and perhaps Kyrgyzstan) into Uzbekistan – in other words, through Sogdiana – and from there into Turkmenistan, Iran, Iraq, Syria.
This does not show an alternative southern route which began near Kashgar and passed through Bactria, north of the Hindu Kush, before rejoining the main route north of Merv.
Another road left China to cross the Karakoram into what is now Pakistan.
The Silk Road is not a steppe route. It runs south of the steppe. It is a mountain and desert route.
On the other hand, from Transoxiana, traders could pass north of the Aral and Caspian seas in order to reach the Black Sea ports via the steppe.
Buddhism entered China on the Silk Road via the Kushan Empire in the first century of the Christian era.
The salt lake at the eastern edge of the Taklamakan is Lop Nur.
The Dzungarian Gap is the approach, between the Altai to the north and the Tien Shan to the south, across the now-Chinese Gobi, to the Great Wall and China proper.
China’s artificial northern frontier was the Wall. Its natural northern frontier was the Gobi.