Cable 'thickness' or gauge, usually matters with power going through it. This creates voltate drop at the delivery end. A toaster requires power. A sunlamp requires power, So does your electric drill or sander. Radios or in this case audio speakers so not use very much power, so voltage drop is not an issue unless you're going a long way. What is a long way. That article mentioned above using a quarter mile as an index of when you have to worry about voltage drop might be a bit extreme, as that is 1,320 feet. But if you buy mains cable and keep it inside a normal house, you can probably trust it to do the job from one end of the house to the other and back.
The audiophile wire they used to sell was a triumph of marketing over physics. And the math is simple: Ohm's Law: E/R=I. Interpreting the maths, well . . .

And if you are terminating the wire where you have bare ended wires going into some kind of spring loaded capture thingy, you want all the wires to fit in there, not giving them a 'haircut'.

When it comes to passing digital signals, you DO care about cabling type. In that case, the nature of the signals and terminations and lengths all matter much more than in the simple speaker wire issues of this thread.