Smoke alarm will not stop chirping?
They way you describe this, sounds like you have a sensor that you are going to wire into the circuit to control an existing light. To do this, you would need to take the feed from the existing light to the sensor, then return a new feed from the sensor to the light. If you have a new light WITH sensor arrangement, then you should be able to simply swap out an existing outside fixture for the new fixture. If for some reason this is not possible, I suggest you hire an electrician to mount and feed the light.
Pipe is none flexable as in steel pipe or sprinkler pipe. Although sprinkler pipe is somewhat bendable. Tubing is usually coiled and in some cases very flexable. Tubing can be used for different air product delivery and or vacuum where pipe in your house is in the wall used for plumbing of water, gas, sewer, etc. Pipe lasts longer than tubing. Hope this answers your Q.