...on chains for a 6X2 12 speed.

While it was a wonderful time in my life when Sedisport came out with those bushingless chains, that worked so well and couild be purchased so cheaply in bulk rolls that I stopped cleaning them and just replaced them and threw away the old ones, those days are long ago. Sedisport chains from the used online sources command impressive prices now (especially considering the original price), and they work no better than a KMC 8.93 x plate chain that can be had brand new online for about 12 bucks. And I have used both.

My only other advice would be to use blue Loctite when installing your fixed cup (if you don't just go with a sealed unit in the BB). Sometimes I even use Loctite on the sealed unit cup on that side, if it's made from aluminum alloy or has anything else that might squeak if it loosens. This is only what I do. There are obviously other opinions. Cables and housings are all pretty good if you go with plastic lined housings and stainless, die drawn (smooth) cables. Can't say I notice a difference.