Set the render disks to the fastest available non systems disk, there will be audio and video render, put both in same place.
Set the capture disk to the slower USB disk, and copy your camera files here, and take them into premiere from here.
The main thing is that premiere is pointing the renders to the fast drive.
64gb isn't an awful lot of space. If your system is running happily from the 64gb then let it be, use the new bigger one for renders. They pile up when you start making changes, adding colour correction, text, tweaking audio etc.
You can always trash renders once your project is completed and you have a high quality finished version.