It's all computer controlled. You can program it to never leave first gear. You can change the upshifts at WOT, you can change the shift pressures to firm them up, you can change how/when the torque converter locks, you can probably change the downshifting or upshifting based on TPS and engine load, etc.
Not are tunes are equal, you definitely want to find someone who knows what they are doing and has done many of the same transmission.
James Henson did a great job with my sport trac (5r55e). But when he tuned my F150 the shifting was horrible, way worse than stock. After 3 or 4 different tunes they are improved, but I'm still not happy with them. I got tired of the back and forth with emails and phone calls to try and fix it. In his defense he did make a good effort but I wouldn't recommend him to someone with an F150. Some day I will get new tunes from someone with more experience with F150's.
2006 F150 FX4 Super Crew - Bilstien 5100s leveled 2", 35" KM2s, 4.56 gears, Detroit locker, Eaton E-Locker, Traction Bars, AEM intake, Xcal 2
2010 VW Golf TDI 6MT