This list might give you some ideas:

https://water.tamu.edu/best-shrubs-texas/

Look for the sun/shade or shade, and 7 (adaptable to most of our state).

When you say you want a screen + foundation plants, though, do you mean right up to the windows? Do you have room to plant them farther away? Can you post a pic of the area? I'm not sure what height, width, etc you're wanting.

Of those two you mentioned, I'd go with the Sky Pencil. The yew will stay pretty low, not sure it would be enough privacy. And the SP would be an instant solution, depending on the size you buy.

There is a newish variety of Yaupon, "Scarlet's Peak" ... stays narrow, but it does get up to 20 ft, and I don't know how much shade it can take. The females have berries.

You might want to check around at trusted, local nurseries and get their opinions. Take pictures to show them.

Another option is a trellis, arch, etc, and growing a vine(s) on it. Or, if you don't find a suitable plant, cafe curtains on the lower part of the windows.

How much distance is there from the window to your property line? I'm just wondering why you need something so narrow, and am trying to visualize the area. Is it your side yard?

Maybe a lady slipper succulent. Ours grows about 5 ft. to 6 ft. tall and is very hardy. We're in Zone 8. It flowers in the Fall.

We're using nandina as a narrow screen for a similar exposure problem in our north side yard. Will thrive in full shade, though with somewhat less color variation and slower growth. Compact nandina (Nandina domestica 'Compacta') is a bit smaller cultivar. The 4 ft tag height can be maintained if the tallest canes are occasionally pruned out, otherwise it will eventually grow to ~7 ft.

We've also used tall canna as seasonal and temporary screens. They flower less and stay a bit narrower in heavy shade, but some will still work there as a quick and inexpensive privacy screen.

This Dutchman's pipe vine gives us complete coverage. There is complete shade underneath where we started it but it soon outgrew the shady area.