oh gosh,

synchronous, asynchronous, isochronous, plesiochronous describe the physical interface and doesn't have anything to do with the transmitted payload.

synchronous transmitters/receivers have at least a seperate dataclock, sometimes even a frameclock.
all other variants recover the tx/rx clock from the dataline.
Standard 10Base-T/100Base-T or even 10Base-2 is asynchronous.

Framing protocols like HDLC is not bound to a specific transfer mode, you can use it on a byte oriented UART as well as on a bit oriented DSL EOC.

In a TDM/PCM Highway for instance you have a frame and clock signal, so there would be no need to encapsulate the payload.

Cheers, Roger