On the web page that advertises the MOBO, the ThunderboltEX # is recommended to anyone who wants lightning fast transfer rates. https://www.asus.com/us/Motherboards/PRIME-X299-DELUXE-II/
Go 3/4 of the way down the page:
Thunderbolt™ 3 port
Experience blistering Thunderbolt 3 speeds and...
I just purchased The ASUS ThunderboltEX 3 PCI card and, to be honest, the directions SUCK. This card is recommended by the manufacturer but they don't provide detailed install directions. I am looking forward to 40 GB transfer speeds and have also purchased a CalDigit dock to augment the...