I wouldn't think there would be a great deal of strain on steering cables. What I got should have been strong enough but was really too thin for practical handling. Yes it worked, but ... Can't remember if it was any more than 1mm and was only purchased to try it. I will probably go with at least 2 mm but don't see the need to go above 3mm.
Mine will be a single length with the ends secured up front, through two bolts that can be turned to tighten. Further adjustment will be a rare, if ever, affair.