if the question is "how many displays", that is more complex than what you asked.
The Apple standard for its built-in hardware-accelerated displays, makes them suitable for full-motion video 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. This requires a hardware rasterizer/display-generator for each fully-accelerated display, supported by Huge memory bandwidth to refresh each display 60 or more times a second.
With one minor exception, the same rules we learned for the M1 and M2 still apply to the M3 models. Display interfaces are generated deep inside the system on a chip. How many there are depends on the exact type of Processor:
M3 (plain) like the 13-in and 15-in supports up to ONE External fully hardware-accelerated external display.
Except the M3 MacBook Air models with 13 or 15-in display, (and certain M3 plain MacBook Pro models when running 14.6 or later) which can support a second external display instead of the built-in display when you close the cover on the built-in display.
M3 PRO processor supports up to Two fully hardware-accelerated external displays.
M3 MAX processor supports up to Four fully hardware-accelerated external displays.
M3 ULTRA processor supports up to Eight fully hardware-accelerated external displays
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next, you have to decide what KINDs of displays -- do you need all displays to be full motion Video?
If and only if you are doing ONLY program listings, spreadsheets, stock quotes and other slow to change data, there are some other solutions, but they require you to make some strong compromises. You can add some additional "fake displays" that reproduce the picture, but FAR slower than real-time. Each additional "fake" display requires an external "stunt-box" that holds some display hardware to generate the data stream to send to an actual display. Using a mouse on such a display can make you feel queasy.