M4 Mac Mini and two 10-year-old 27" Thunderbolt displays.

From the Technical Specifications for the new Mac mini:

----------

M4

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

----------

If at least one of those 27" Thunderbolt Displays has a good "hydra" cable, you might be able to get away with just a single Apple Thunderbolt 3-to-2 adapter. This would save you $50 and the use of one of your Mini's TB ports.

• Plug the display with the good "hydra" cable into the Apple Thunderbolt 3-to-2 adapter, using the TB head of the good cable.
• Daisy-chain the second display to the first. If the second display has a bad or flaky "hydra" cable, get a separate Thunderbolt 1/2 cable and run it from the daisy-chaining port on the second display to the daisy-chaining port on the first.

Yes..

There has been no mention whether the M4 supports daisy chained video on Thunderbolt and it has been problematic in previous "M" versions of Macs.