Hi jtreble, breakout cable will give you flexibility to connect XL710 QSFP+ to SFP+ switch with downgrade speed of 10Gbps. in the operating system, you should still see 1 Ethernet adapter if you would go with DA1 and 2 Ethernet adapter with DA2.
sharing the product brief of QSFP+ cable for your reference:
hope this help.
Thanks for your quick response.