Can a serial queue be either synchronous or asynchronous?

I’m considering every possible combination of options between serial and concurrent, and synchronous and asynchronous. I can only think about so much at a time. At this time I’d like tons if a serial queue can be either synchronous or asynchronous? I assume if they can be either one of those, a queue would have to be one or the other during its lifetime. I’m taking slow. Please try not to share too much with me when you answer.

The two are separate. The queue types determines whether that thread the queue is working against can run one job at a time or multiple.

The sync/async determines what the current thread does during submission to the queue. Does it wait (sync) until the job has completed before the current thread moves on, or does it “fire and forget” (async) into the queue.