As to "run[ning] extensive audio workstation software (Logic Pro) smoothly," if you install the OS on the SSD then it will load programs faster but probably not do anything for you while the program is running. The audio workstation software is more likely disk bound on the data or cpu bound.
If your OS will fit in 30 GB, by all means install it on the SSD with the faster read rate. You may be able to improve your audio sessions by attaching the other SSD, with faster serial write rates, and copying your current project to it. If the process is disk bound, reading input and writing output to the SSD may give you an improvement. Then again, it might not. Try it.