As far as the 2x, that’s not terribly surprising. Sharper pixels don’t necessarily do the GC any favors, so the smoothed upscaling provided by your TV might look better. I am on the fence about it on my TV.
As far as RGB range, to my knowledge it always outputs full range RGB. If your TV can display full-range RGB, then you’d want to set it to that so that the color space matches.