<< if an upgrade will/can support the use of 2 monitors with the MacBook Pro (2020, 13" >>
there is no such upgrade forthcoming
The 13-in Apple-Silicon M1 MacBook Pro and Air are extremely-capable entry-level computers. They can support the internal display AND an External display up to the previously unheard of size of the Apple 6K display at billions of colors. But only ONE in addition to the internal display.
This may not match the way older computers forced you to work, since older computers were not able to support a really large external display. But it is NOT a defect. The spec was available long before you could purchase the computer.
Fetching screen data is done by rasterizer/display-generator Hardware in the graphics subsystem. Once set up, data are fetched at that same interval again and again without additional intervention. The entire screen data MUST be completed within each screen refresh interval (often 1/60th second) or the screen will go partially or completely blank without the late or missing data. In addition, each one-pixel-tall Row must be fetched on a much tighter schedule within one row-time, or part of the row will be blank.
This is the Apple standard for its built-in hardware-accelerated displays, which are suitable for production/display of cinema-quality video with NO dropped frames, and NO dropouts or partial-blank scan lines due to memory under-runs or other issues.
--------
There are aftermarket docks and stunt boxes available that use DisplayLink technology. DisplayLink technology creates a "fake" display buffer in RAM, sends the data out over a slower interface to a stunt box with DisplayLink custom chips that put that data back onto a "legacy" interface. It is not a true "accelerated" display, and it can suffer from lagging. Just adding the DisplayLink Driver is not adequate to get a picture -- you need a DisplayLink "stunt-box" or a Dock that includes DisplayLink chips.
It may be acceptable for a second display showing slow-to-change data such as computer program listings, stock quotes, or spreadsheets, but NOT for full motion Video, not for Video editing, and absolutely not for gaming. Mouse-tracking on that display can lag, and can make you feel queasy.
In a pinch, it may even play Internet videos (as one user put it) “without too many dropped frames".