there is still a bug open regarding latency compensation for audio
However, someone gave me a hint to tune the system to keep latencies
low. The -p parameter of jackd should be as small as possible (try and
error). I managed to decrease it from 256 to 64 (must be a power of 2).
Now latencies are hardly noticeble. With 256 I had to re-align audio
tracks when inserting some plugins (anywhere, not only in audio tracks)
like 10 band EQ or autotalent.