I'm currently using TSI3 so would also be interested to hear if anyone has had a proper Titleist fitting into the GTS lineup and what feedback they have

I have been switched a couple of times from 2 to 3 and back to 2 on different models. I try not to go into a fitting with a preconceived idea of which head model I need. I let the fitting numbers and feel ultimately determine which one I select. Doesn’t matter if it’s the most common head or the least common head. All that matters is what works for me. Best wishes on your fitting and hopefully many enjoyable rounds with the new driver.