All of Cathay's aircraft have PTVs in economy, except for the 3 A340s leased from Air China. Denpasar is normally operated by an Airbus, with possibility (Unfortunately for you) that it could be one of the 3 Air China aircraft.
As for a strike, it would be unlikely. Perhaps expect some delays. Hopefully you do not have tight connections, otherwise you could end up missing a flight. Delays of 1-2 hours are not too uncommon.
Spotting at CLK depends on whether they are using Runways 07 (From Macau/China direction) or Runway 25 (Over Hong Kong). If they are on 07, then from Tung Chung (The town next to the airport) you can take the S52 bus from the bus terminus and get off at the last stop. Don't take the S52P, as that goes somewhere else. To get to Tung Chung, take the S1 bus from the airport and get off at the large bus
If they are using 25 it is easier. Go to the Airport Hotel and walk outside the main street-level doors. Cross the road and walk to the right, then left. Behind a small grey building is the sea. Just sit there are watch planes come in. Unfortunately you cannot see departures from here.
If you stay airside it is good as there are large glass windows everywhere to watch from.
Hope you enjoy your trip and have a few good flights!