While you're waiting for some replies you might want to check out these posts on growing trees for screening.

'Blue Ice' Arizona cypress
is one that could fit and do well in your area. Eastern red cedar
could also work, but don't know how well adapted any of the
fastigiate/dwarf cultivars like 'Brodie' are to the hill country.

Suspect Boerne soil is probably too alkaline for the several pond cypress cultivars that grow ~12 ft across and ‘Slender Silhouette’ sweetgum used elsewhere in Texas. Plus they're native to wetter areas, so would likely need more irrigation than other options.

thank you. based on your suggestion and the link provided AZ cypress is now on the list. I'll start looking for them locally to see in person.

Neglected to say congratulations on the move to such a nice area. We really enjoyed our side-trip there for lunch on Cibolo Creek a few weeks back.

Don't know of a fastigiate crape myrtle cultivar, but they can be trained to many shapes. The two full-size multi-trunked CMs in our narrow side yard were trained from 3 gal size to fit within the 10 to 14 feet between our house and the fence - without resorting to "crape murder". Generally prune twice a year to train and maintain.

There are some very nice Italian cypress and Thuja in Dallas, but they are not often highly recommended here. Would proceed with caution if there are not any good examples growing in your area or not recommended by a good local nursery.

Thanks again. I was looking for a Cypress or evergreen so the AZ Cypress sounds like a good fit. I'll also look for the Red Cedar you recommended. Crepe Myrtles are great (but messy) and certainly forgiving but they were going to be my last resort. I am wary of Italian Cypress after word searching this forum and finding what seems to me to be very seasoned gardeners asking for help on them.