The protocol plans around round times drastically changed. We (Second) are currently thinking about 1 hour rounds, more or less. But you would only use rounds to refresh your own VTXOs when they are about to expire. To send payments, you can your arkoor or out-of-round transactions that are instant. (But don't worry the above signet Ark server does rounds every 10 seconds.)

When it comes to doing coinjoin rounds, that's currently not implemented.