Those are relatively far if he plans to reside in Plano. My parents used to go to Hong Kong all the time until their produce quality started going down.
If you're into banh mi, there's a shop around Hiep Thai that makes some kickass ones. Buy 5 get 1 free. Too bad Lee's Sandwiches just closed in Saigon.
99 Ranch has a great bakery. Other than that it's a tossup along with Asia World, just go to whichever has a better price. For restaurants along the Asia World strip, skip Umeko (overpriced IMO), do go to Que Huong for pho, and do go to the Sichuan place. There's also Shui Wah, but my parents know the owner and think she's kind of letting it get a bit stale. Food there is pretty oily and the service is slow.
On the 99 Ranch side, there's a restaurant called Mian Cuisine, serving Taiwanese (I think) cuisine, but they've changed owners at least twice already so I have no clue what the food quality is like now
Dallas is full of fatties