Been training BJJ in DFW for 6 years now and have dropped in at probably a dozen gyms. Quick rundown of what I've seen.
Fortis MMA in Deep Ellum is elite level but you're paying for it. If you want to compete seriously it's probably the best room in Texas.
Gracie Barra locations are everywhere and the curriculum is consistent but some people don't love the mandatory gi rule and having to buy their branded gear.
For striking, Lonestar Muay Thai in Arlington is underrated. Small gym, killer coaches, no ego.
My biggest piece of advice for beginners: try 3-4 free classes at different gyms before committing. The culture matters more than the name on the wall. Some expensive gyms have toxic vibes and some hole-in-the-wall spots have the best training partners.
Title Boxing Club is great for fitness. If you want to learn actual boxing technique, find a traditional boxing gym instead. Different goals, different gyms.