If you absolutely don't care about optimizing lookahead, which is basically the most important thing when you're like at the high levels of cubing, and want to get really lucky scrambles, then pick full CN, tho, full CN in Roux is really hard imo.
I can see that lookahead will be obviously really superior in x2/y CN cause you're not looking to improve at like 24 blocks which is insane.
I can maybe compare it like this, give a beginner who is not good at lookahead when CN but is really good at lookahead when it's not CN (unrealistic I know for a beginner but this is true for any method, lookahead in full CN is << lookahead in x2/y CN) a really lucky scramble, prolly had FB + DR already there, sure there's pieces solved = good lookahead right? well it's not that many pieces to compensate a lootttt of pauses during maybe SB and other unsolved pieces,
and FB + DR is not common imo.
but on the flip side, chances of a lucky scramble like FB is there becomes better than x2/y CN as you have a lot of choices for blocks.