Looks similar to the unbranded cables I am using. If possible I’ll recommend contacting or popping along to your local electrical store or dealer as you might be able to pick up unbranded 79 strand cables for not much money.
No speaker cables do not have to be the same length, you might find a time where you can move speakers so they are equidistant from the amp, and then you're stuffed with one short piece of speaker cable that is useless.....
If you are any good with a soldering iron I would recommend getting bare wire cable ends soldered.
As others have said, QED79 strand is perfect - don't worry about branding marks on the cable, as it does not affect the sound.
Although copper will tarnish over time, as long as the speaker terminals are tight and compressing the wires of the speaker cable, then the contact area will not tarnish.
I twist the 79 strand into three separate strands, one goes through the speaker terminal hole, the other two around the sides, and twisted all three together at the top, and cut off the extra very near the speaker connector - so there are no stray single wires.