There is TSA Pre-Check in Terminal B. Or at least it is Pre-Check Lite during all but the slowest hours. Located approximately Gate 28-29.

Dedicated line and agent kiosk. They hand you a TSA card. Traffic flow past there is laid out oddly and the lines cross each other. People get confused. The lines get confused. Infrequent flyers really get confused. But Pre-Check is there.

It is the most logical entry point if you arrive on light rail from Tarrant County. It is generally still less crowded than the alternatives. Most of the time. Unlike most of DFW TSA kiosks, you still have to show both a boarding pass and Gov't. ID.

If there is a Flagship Lounge in Terminal B I'm not aware of it. But then again I don't have the exalted status to be worthy of entry, so I really don't know.

The AAdmirals Club in B is a pleasant place and quieter than the DFW big three clubs. But it is small and has reduced offerings.