I don’t think 3d printed letters are a “professional” option. The finish isn’t smooth unless you use acetone to smooth it, or use a filler and sand it smooth then repaint. That’s the only way I feel you can achieve an acceptable professional product.
Additionally, you’ve now limited yourself to producing indoor only products. These won’t last outdoors. The material (abs, pla, etc) is designed to melt at low enough temps to allow it to flow through nozzles of a 3d printer. That means their structural integrity is lost when the sun hits them. They won’t melt but it’s enough to warp them.
A laser cutter is an alternative. It’s not as much as a cnc in most cases, but is more than a 3d printer. You’re still limited to cutting simple shapes rather than being able to use a cnc and producing any 3d shapes/curves you can design.
Have you used a modern 3d printer? The klipper firmware makes the prints pretty smooth... Its not as perfect as acyrlic, but if you're doing outdoor large letters, you won't notice it.
Petg works great for outdoors. As does asa.... I don't know if its hold up to Texas sun, but both are rated up to 90c... Which is hot, if it were attached to a metal frame... Might be an issue, but I've never seen petg or asa warp.