What video resolution and refresh rates does this cable support?

It supports DisplayPort 2.1 with DSC, up to 8K at 60Hz or 4K at 240Hz.

What is the maximum data transfer speed of this USB4 cable?

This cable supports data transfer speeds of up to 40 Gbit/s.

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StarTech 1.5ft (45cm) USB4 Cable, 40Gbps, USB-IF Certified USB-C Cable, 240W, 8K 60Hz/4K 240Hz DP2.1, Thunderbolt 4 Compatible, White

Mfr Part#: CC18IN40GUSB4TPW
UPC: 065030923712
Length: 1.5 ft (45cm)
Data Transfer Speed: Up to 40 Gbit/s (USB4)
Video Support: DisplayPort 2.1 with DSC, up to 8K 60Hz / 4K 240Hz
Power Delivery: Up to 240W USB-C Power Delivery 3.1 (EPR)
Color: White
Certification: USB-IF Certified, E-marker Firmware
Compatibility: USB-C and Thunderbolt 4 Laptops, Docks, Monitors, External Storage
Warranty: Lifetime
Country of Origin: Vietnam