I am arriving at Tongren airport at 8:50pm and would like to travel to Fenghuang.

There is no other mode for your choice. You need to take a taxi, and the fare is about CNY100. Well, if you want a more economical mode, I suggest you carpool the car with other passengers. Once you arrive at the airport, you can easily find a lot of companions who share the same route and destination with you. Good Luck.