A faster HD allows faster project/plug-in load times, higher audio track counts and better performance from plug-ins that stream samples (n.b. nothing bundled with Platinum streams samples) only. Latency is affected by audio driver buffer settings and plug-in delay compensation NOT hard drive characteristics. There is no real performance advantage in moving templates or anything else in "Cakewalk Content" or the user directory to a faster HD.
While it is is possible to to change the default project and global audio folder keep in mind, if SONAR starts up and the drive is not found, SONAR will change the preference settings back to factory default settings.
Assuming you are using per-project audio folders, it is easy enough to create projects and stream project audio to/from any drive available to a PC without making any preference changes.