If the project sample rate in Audacity is set to 44.1kHz and I import audio at 48kHz, does it get converted right away to 44.1kHz? Or does it stay at 48kHz until export, so I can change the project sample rate whenever I want?
The project sample rate only affects playback and recordings/generators on newly created tracks. Imported files keep their original sample rate, and the default sample rate for exporting is the highest track sample rate found in the project.