Dear Stéphane,
so many questions, so little time [;)].
Synchronous Processing takes more CPU power - I´m the wrong guy to ask for the technical reason, but I guess that the buffers are adapted in realtime, and this adaptation takes CPU power. I´m not a programmer...
All other questions I will check (or maybe you find a little time to find out yourself... I´m not using FXT in my setup here, so this information may take a little time.
Thanks for your patience!
Best,
Paul
Paul Kopf Product Manager VSL