FWIW Harmy, these are the x264 encoding parameters I used to create a good BD-compatible file:
--preset=veryslow --tune=grain --bluray-compat --fps=23.976 --force-cfr --vbv-maxrate=25000 --vbv-bufsize=30000 --crf=1 --level=4.1 --open-gop --slices=4
The vbv-maxrate parameter can be adjusted up or down to change the bitrate.