Thanks for the advice. I can loop the cable back on the dual port QSFP+ Mellanox card using the QSA and some breakout boards (since I dont have a second QSA) and the Mellanox card links-up at 10G.
The Intel is dual port SFP+ and if I loop the cable back using an SFP+ cable it links-up at 10G.
I'm waiting to hear back from Intel about their expectations for my Mellanox-QSA-Intel configuration.