Depends on what you're looking for… might be too much info, but here goes.
1) More of a tweak to existing plans using a mostly templated approach? Buy a plan online and tweak it with a drafter or use a design/build firm and tweak one of their plans. Some smaller custom builders who aren't "design/build" even have a few existing plans from an architect they know that they use for spec houses. Flat fee and/or baked into cost.
2) You already have a real clear vision, sketches, floor plan layout ideas? Talk to a drafter or maybe an up and coming architect. Typically a flat fee.
3) You have no idea what floor plan you want, but maybe have some design or style ideas via photos and a want it to be more one-of-a-kind? Then go architect. But make sure they e done houses in your style and price point. Some rare ones charge a flat fee, but mostly $/covered sq ft.
In #3, you need to make sure your architect and builder will work together through the process. We fell mostly in #2 I had sketched elevations and floor plans myself), but paid for #3 anyway. It was helpful to avoid some small mistakes but probably not worth the $ beyond trim and cabinet elevations/detail. We used Briggs, but interviewed many, many more. We were generally happy with the final product, but most architects are creative types and not great with the project management/communication and it can take forever if you don't stay on them.
Here are the firms that made it past our initial cut after we interviewed probably 10 - would've felt comfortable with any of them handling our design. Happy to send over pricing/specs if I can find them (from mid 2022) if you want.
Briggs Architecture
Larry Boerder
Lloyd Lumpkins
Richard Drummond Davis
Stephen B Chambers
In all these cases, make sure a structural engineer signs and stamps any plans, even #1. Worth the $$ and peace of mind.
Either way, depending on area of DFW, make sure you get a full geotechnical report and standalone foundation design (stamped by an engineer) after the house and site plan is done. Our clay-heavy soils need special attention.