To be able to optimise performance and spread the workload over multiple processors, Logic uses larger buffers. The “multithreading” selector selects when these larger buffers are used, and “process buffer size” determines how big those buffers are.
“Processing threads” seems to max to the amount of cores you have in your computer.
If you select: buffer=256, processing threads=2, process buffersize=small, multhreading=playback tracks, the effective playback buffering = 512.
If you change threads to 8 here, the playback buffering will be 1024.
Now change the process buffersize setting to large, and you’ll have a buffersettings way over 1024…
As long as “multhreading=playback tracks”, a live track (recording enabled) will use the principal buffersetting (256).