From capital airport to Wangfujing area (hotel Novotel Peace)

You can take airport shuttle bus line 13 to Jinyu Alley, and then walk to the hotel. It would cost CNY24 and take about an hour. Only two buses are in service for this route, at 11:00 and 13:00. Hope you can catch that.

If by subway, you can take the airport express to Dongzhimen. Take subway line 2 to Yonghe Palace, transfer to line 5 to Dengshikou. After getting off from exit C, walk to the hotel. It cost CNY28 and take 40 minutes to reach.

For the back journey, you’re suggested to take a taxi. You can get off from the hotel at 10:30pm, and then you may arrive in the airport at about 11:30pm. You’ll have enough time to check in. BTW, the taxi fare would be around CNY130 at night.

Can I use bus line 3 (it is often), from airport to downtown and after that use taxi to hotel ?
What is daily taxi price from airport to downtown ?

Yes, you can. Take shuttle bus line 3 and get off at Yaobao Road or International Hotel. Then the distance to your hotel is around 1mi. The taxi fare would be no more than CNY15 for such a short journey. If you take a taxi directly from the airport to your hotel, the cab fare shall be CNY90-100.