crf encoding is a no brainer, but yes, increasing ref above 8388608 / (width*height), ie. 5 for 2:35 cropped 1080p, would break absolutely everything from GPU-assisted playback to every standalone player for practically no benefit other than a minor increase in compression efficiency.

x264 is perfectly capable of producing transparent encodes without breaking compatibility,, and the jump from the 2-pass fit-to-bitrate AVCHD-complaint version to a consistent quality crf encoder would be much higher than the jump from a that crf to some ridiculous set of "crank everything to 11" settings.