MacBook Pro 2020 (M1) Clam Shell Dual External Monitors?

I just recently purchased the M1 MacBookPro17,1 at the highest cpu/ram spec offered at launch (8cpu-8gpu/16gb) and tried this scenario.

It appears to only support one monitor at a time in either clamshell or open. Both monitors function one at a time, but not at the same time.

It also appears that the refresh rate is capped at 60hz. I was able to drive the same screen from my mid-2018 MacBook Pro w/ at 1440p@144hz, but I only ever did so with a Vega64 eGPU. That said, the spec sheet for the M1 never claimed it would do more.

I’ve heard anecdotal evidence that a display link adapter will work, but i’ve not tested it.

For background information:

There are "fake" display options that could be employed to allow connection of an additional limited display, if you do not need the fully accelerated performance of a built-in hardware-accelerated display. Most of these options require an external stunt-box or Dock device [from many different Vendors] and an internal Software driver by DisplayLink.

Some Dock devices already contain these items, and do not explain that their "second" supported display is not a fully-accelerated display. In my opinion, that is indefensible, bordering on fraudulent.

Such a display would be adequate for slow-to-change information like stock quotes, program listings, spreadsheets, PERT charts, and presentations that do Not contain movies.

Such a display would NOT be adequate for full-motion video or anything that requires substantial GPU computation, such as playing or editing Videos or Editing Photos or modeling of any description. It would be questionable for any activity requiring a lot of mouse-tracking on that display, because it may be less -responsive than desired.