This *seems* to be the settings to use for the best BD compliance: (EDIT: modified to follow --fullhelp settings order)

x264 --profile high --preset veryslow --tune film --keyint 24 --min-keyint 2 --bframes 3 --b-pyramid strict --open-gop --ref 4 --cabac --slices 4 --bitrate 23000 --vbv-maxrate 40000 --vbv-bufsize 30000 --pass 1 --stats ".stats" --weightp 0 --merange 24 --overscan show --colorprim "bt709" --transfer "bt709" --colormatrix "bt709" --nal-hrd vbr --output NUL "AVPR_final3.avs" --sar 1:1 --level 4.1 --bluray-compat --aud

x264 --profile high --preset veryslow --tune film --keyint 24 --min-keyint 2 --bframes 3 --b-pyramid strict --open-gop --ref 4 --cabac --slices 4 --bitrate 23000 --vbv-maxrate 40000 --vbv-bufsize 30000 --pass 2 --stats ".stats" --weightp 0 --merange 24 --overscan show --colorprim "bt709" --transfer "bt709" --colormatrix "bt709" --nal-hrd vbr --output "AVPR_final3.avs.264" "AVPR_final3.avs" --sar 1:1 --level 4.1 --bluray-compat --aud

assuming that the avs file is perfect, here is what I'm going to do for the latest test:

x264 command line (pass 1 and pass 2) to obtain the encoded file as .264
EasyBD Lite to make a compliant BD, using .264 file and all audio and subtitle tracks
result 00001.m2ts file will be used to feed MultiAVCHD
if final 00001.m2ts file is different from the previous one, it will be replaced using the one made with EasyBD Lite

This is because it seems that TSmuxer doesn't mux well video encoded with b-frames - so at the end, THIS should be the cause of jerky/stuttering video, and not CABAC - while EasyBD Lite seems to be the only free tool AFAIK that is able to mux video with b-frames and still be BD compliant; as using --b-frames 0 will waste a lot of bitrate (maybe up to 25%), I'll try this route first.

OK, going to do this; it will take "only" a day, so be patient for the next reply! (^^,)