Can I use a Thunderbolt 4 dock with a USB-C laptop?

Yes, with reduced functionality. USB-C laptops will get USB 3.2 speeds (not TB4 40Gbps) and may be limited to one external display.

Do I need Thunderbolt 4 for dual monitors?

Thunderbolt 4 guarantees dual 4K display support. USB-C docks may support dual displays through DisplayLink, which uses software-based rendering.