The traditions and culture in Tajikistan are different and similar at the same time, the same as it is in many different countries all over the world. But Tajikistan is a small mountainous country and many of its spots and areas were quite isolated (some areas - very isolated) just before the 20th century.
The flat areas and big cities were often times under "press" of continue invasions of different cultures and ethnics. As result,
You may see people with very different features, from Mongolian (North, North-West and South) type to typical European (Kohistan, Badakhshan). Definitely, the Tajik culture had some influence of other cultures, but in its origin this is a culture
of Iranian people; in language, music, behavior, architecture and etc. At present, it is much related to so-called Islamic culture, although there are still remains of pre-islamic culture, which is "adapted" to Islamic traditions (such as deep trust in holy places - mazars, and Holy Spirit; "clean" and "unclean" animals and men, solar symbols in handicrafts and traditional clothes, traditional architecture and etc.). In Soviet time many traditions were almost disappeared. So, many historical and traditional things might be seen in museums only.

The traditional food is also changed in last 50-60 years. Traditionally, the Tajik people, especially from mountain areas
used lots of vegetarian food. There were many different sorts of noodles (made from peas, wheat, oats, and beans) and porridges cooked in different way and methods. Often times, the porridges were mixed with different dry fruits (like Musli),
collected during summer and autumn. Probably, the moist popular was mulberry trees and fruits. There are many different sorts of mulberry grow in Tajikistan (as well as Afghanistan and Iran). Tajik people are traditionally good gardeners. The Iranian (Tajik) gardens were well-known from ancient time. The word "paradise" also comes from old Iranian language: when Greeks, leaded by Alexander the Great saw the gardens, they were very impressed of the gardens beauty and asked the locals, what is that? As they didn't understand the language, they answered: U-para-diz, that means - what's over walls (e.i. fortress).
In big cities, like Khujand or Samarqand, people cook almost the same variety of food as in neighboring countries: Manty, rice pilaw, soup with meat and vegetables (Shubo/Shurpo), lagman (noodles), kebabs (kabab/shahslyk), Sambusa (Samsa) and etc.
It is hard to say what is traditional and what was introduced, because these cities were situated on the Silk Route between China and Iran, but very obviously that the Chinese (as well as many others) had their small traditional restaurants all over the road.