PVC Is poly vinyl chloride; a tough plastic made of carbon based chemicals (oil); I am not sure what PE’s chemical name is, it is tough and can be made of oil too. PVC tubing and pipe comes in sizes from around one half inch to several inches. PVC is generally not flexible and must be joined, sealed with a sealing solution. PE Pipe and Tubing is generally small tubing and pipe, from tiny to one and a half inches or so. The PE that come with the drip/sprayer kit is about three sixteenths of an inch in inner diameter. The tube is black, so it must be covered over or it will show. It is great for small and large jobs, over about a quarter of an acre, to patios. Generally there a no local codes for PE whereas there are for PVC. PE is about the flexibility of a ten inch tie wrap. PE is not meant to be left “on” for long nor unattended, Whereas PVC is meant to left “on.” Some of the new piping for houses is PE. It is not the Garden variety PE. it comes if red ad blue colors and is known for being “freeze Proof.”
I buried my PE over a one quarter acre lot and have bout 10 sprayers on it. I placed the system on a timer and set it up with tie wraps securing the joints. It functions great! I feel I have a lot less problems with it than I would a PVC. If a side joint fails the system still works. I only buried the tubing one inch; you can’t do that with PVC. As for a patio or garden I am sure the tubing will serve as great. PVC will last a long time. PE will last somewhere less that ten years

Yes. I added this to my existing system. I see no reason that you couldn’t purchase a second kit to continue expanding

100ft | 30m of tubing is provided in this garden irrigation system