1. The taxi fare would be around HKD230 from the airport to Tsim Sha Tsui(https://www.travelchinaguide.com/attraction/hongkong/kowloon/tsim_sha.htm). The cheaper way may be to take bus A21 from airprot to Tsim Sha Tsui, it costs HKD33/person. It is the traffic peak time at 6pm, thus there may be traffic jam.
2. You can take bus 90c from Aberdeen Tunnel Toll Plaza to Jardine House, Connaught Road Central, then transfer to bus 1 from Connaught Road Central, Outside CityHall Carpark to The Peak( Public Transport Terminus). When back to Peking road, you can take bus 15 from The Peak to Central Pier 5, then take ferry from Central Pier No. 7 to Star Ferry Pier (Tsim Sha Tsui). You can walk to Peking road from the ferry terminal.
3. It may be OK for you to visit the two places in one day. From the buddha to Cheung Chau, you can take bus 2 from Ngong Ping Bus Terminus to Mui Wo Bus Terminus, then transfer to ferry from Mui Wo to Cheung Chau. It costs about HKD30.