"Not chosen because of old driver" Premiere pro CC 2019

You will have to go back to CC 2018 (12.1.2) with that Fermi-generation GPU because NVIDIA has already EOL'd all Fermi-generation GPUs - including your GTS 450 - for all future drivers and support with the last WHQL driver (391.35) being released back in March of last year. Beginning with the next WHQL driver release, a Kepler or newer GPU is required just to even use. And Premiere Pro CC 2019 requires a driver with CUDA 9.2 or higher support - this means 397.64 or higher WHQL drivers, which now no longer supports your GPU - to even enable CUDA GPU acceleration at all.