Cable lock only = bye bye bicycle
In one way, cable locks are really bad, because they give a false sense of security.
A proven way of more secure locking starts with a high-quality (not cheapo brand) U-lock or a high-quality chain ($50+). A cable can be a useful accessory to make it more annoying to try to to pinch components like seats, wheels, etc.
Depending on what type of main lock you use, an additional cable lock may add extra security insofar as it may take a 2nd type of tool to defeat, and not all potential thieves will be carrying both.
If you're worried about insecure bike racks (which a lot of them are), good! A lot of them are cheap and easy to cut, or have bolts that can be undone, or the whole thing can be lifted by 2 guys into the bed of a truck. Find the secure racks, or find something else to lock to.
I suggest you listen to what
Hal Ruzal has to say about the subject. And some woman from a co-op in Toronto, if you keep watching the sequel videos.