Can I use two Thunderbolt displays with Mac mini

Congratulations. I too have preordered a Mini with the M4 Pro.

The short answer to your question is yes, the base M4 Mini should have no problems with two Thunderbolt Displays.

You would probably need to connect them to two of the Mini's TB4 rear ports. But you can always try them connected in series just to see.

For your assurance - I am using my MacBook Air M3 - which could support dual monitors:

Here is my set up - daisy-chained two TB monitors together (of course, the first was connected to MBA with TB3/TB2 adapter).

Since TB Displays use TB2 to negotiate data (up to 20Gbs) - that dual TB displays is feasible with my M3 device.

M4's TB3 (40Gbs) and M4's TB4 (120Gbs) can definitely manage old TB Displays.

Mac mini (2024) - Tech Specs - Apple Support

"Apple M4 chip

Simultaneously supports up to three displays:

• Up to three displays: Two displays with up to 6K resolution at 60Hz over Thunderbolt and one display with up to 5K resolution at 60Hz over Thunderbolt or 4K resolution at 60Hz over HDMI
• Up to two displays: One display with up to 5K resolution at 60Hz over Thunderbolt and one display with up to 8K resolution at 60Hz or 4K resolution at 240Hz over Thunderbolt or HDMI"

So a M4 Mac mini with a plain M4 chip can drive a pair of Apple Thunderbolt Displays (27-inch) (model A1407). It would be even possible to connect a third display, (but NOT one with 8K resolution or a 240 Hz refresh rate) at the same time.

If at least one of the Thunderbolt Displays has a good "hydra" cable, you should be able to figure out some way to daisy-chain both displays from a single Apple Thunderbolt 3-to-2 adapter. If both of the displays have bad / flaky "hydra" cables, daisy-chaining will not be an option, and you will need two adapters (along with two TB 1/2 cables for bypassing the permanently-attached ones).

Correction: TB4 is still 40Gbs -- TB5 is 120Gbs

You will also need the TB2 to TB3 adapter.