new macbook pro display options

You do not have to get the 16 inch for the M3 Max CPU. The 14 inch can be configured with it as well.

However, there is a difference in what they can support when it comes to external displays.

The M3 Pro chip can support up to two external displays.

The M3 Max chip supports up to four external displays.

This image is from Apple's website:

Yes, "supports up to two/four external displays" means two/four screens +1 if you include the laptop display and you can configure them however you'd like. Mirrored, extended, etc.

You can get pretty much any M3 Pro or M3 Max configuration in either the 14" screen size or the 16" screen size. It's just a matter of custom-ordering a machine, instead of going only with one of the 'stock' configurations.

The (plain) M3 chip is only available on the 14" MBP.. The plain M3 version of the MBP can support two external monitors, but only when the lid is closed, and with restrictions on Retina scaling modes available for a second 4K monitor. (It originally could only support one external monitor period, but a Sonoma update provided the limited second display support found on the M3 MacBook Airs.)

If you know you will be using two external monitors, I'd suggest going with a M3 Pro or M3 Max chip.