ask me how I know... Fuel lines,brake lines (manual 4 wheel Disc, not power assisted due to pressure limits for nickel copper line), and trans lines all Nickel copper on all my vehicles.
Copper nickel brake tubing meets all ASE specs for automotive brake line. I have no qualms about using it in any auto brake application.
I would use ni-cop before using stainless. Stainless (in my opinion) is too hard. Hard to flair, hard to bend. But it does look nice, and will not rust, but neither will Ni-Cop.
PS: Whenever I make new brake lines, I almost always install the "armor" over the tubing. Amazon product ASIN B015YGRG4C
