M4 MacBook Pro dual 240hz 1440p displays?

MacBook Pro (14-inch, M4, 2024) - Tech Specs - Apple Support

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Simultaneously supports full native resolution on the built-in display at 1 billion colors and:

• Up to two external displays with up to 6K resolution at 60Hz over Thunderbolt, or one external display with up to 6K resolution at 60Hz over Thunderbolt and one external display with up to 4K resolution at 144Hz over HDMI
• One external display supported at 8K resolution at 60Hz or one external display at 4K resolution at 240Hz over HDMI

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The specifications seem to indicate that if you connect a 240 Hz display, that comes at the cost of only being able to have one external display.

Likewise for MBPs with the M4 Pro chip. Even with a M4 Max chip, there's no promise of support for more than one 240 Hz display, though with a M4 Max chip, you could have a 60 Hz display or two in addition to the 240 Hz one.

MacBook Pro (14-inch, M4 Pro or M4 Max, 2024) - Tech Specs - Apple Support

There are no docks that can add hardware-accelerated video support beyond what is built into the MBP in question.

Apple does not publish detailed lists going into all possible configurations that each chip/machine supports, or does not support.

In general, bandwidth is not the only consideration. To take one example, while all Mac notebooks with plain M1 and M2 chips can drive a 6K display, none can drive two external 1080p displays.

A 1080p display has only

• About 1/10th as many pixels as one of the 6K displays that these notebooks can drive over Thunderbolt
• 1/4th as many pixels as one of the UHD 4K displays that these notebooks can drive over USB-C (DisplayPort)

and so the "one display" limit has to do as much with the number of display generators on the chip, as with the number of pixels that any particular display generator has to send out on the wire at any given moment.