The jackuser group appears to play the same role as the audio group in other distributions. Sooo only a jackuser group should be created as:
$ sudo usermod -a -G jackuser $USER
and no audio group should be created? The Jack Audio FAQ refers to an audio group. Likewise, I am wondering about the setup in /etc/security/limits.d/95-jack.conf, as again the Jack Audio FAQ recommends setting realtime priority to 95 and memlock to unlimited, whereas the 95-jack.conf file has settings set at
@jackuser - rtprio 70
@jackuser - memlock 4194304
with the memlock setting looking quite odd. Random number?