Sample Rate Converter? This is all beginning to sound like "Liquid Sampling" is coming to your favorite DAW.
I know you can resample from 96k to 48k or 44.1k but can you up-scale from 44.1k to 48k with no problem, or does the DAW handle that? Like if I set my project to 48k, then any lower sample with be upscaled to that 48k?
Yes. Liquid Sampling is quite an appropriate term.
Upscaling is a standard technique similar to downscaling.
It is even a bit easier, as it does not require an anti-aliasing filter. It's just interpolation.
On most DAWs you can import 44.1 k files to a 48 k and they are automatically resampled. And vice versa.
Logic does that same resampling in realtime during recording.