I grew Winter Density in central NM ... it thrived.

The difference is that we have a lot more warm and sunny days, where other zone 7 areas have lower highs and less sun.

I will be growing some smooth-leaved spinach because it gets really dusty here.

For spinach, I like Melody or Bloomsdale Long Standing. I live where it gets cold and I never cover it. It survived 13 below last winter. I have a small fence to keep out the rabbits.

Bloomsdale. Mine lasted through all of winter when planted in fall. Zone 7a, with many hard freezes and snow. I didn't cover or protect at all. They were in large planters. They might wilt and look terrible, but bounce back when it warms up.

My lettuce survives all winter, all varieties, but I use a PVC Hoop house. Worked great.