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I run a 1x10, and there is no problem with chain crossing. The 10/11/12 speed cassettes are basically not any wider than the regular 9 speed ones, so there is no more chain crossing than what you get for the middle ring on a 3x9. The optimization is all in narrower chains and sprockets.

That being said, I do run an upper chain guide to reduce probability of the chain falling off the chainring when the rear derailleur gets clogged with mud etc.

It doesn't seem to be much of a problem on my 1x mountain bike.

It's less crossing than 2x at the extremes