Q: external drives, best practices?

New user, getting ready to download FCP-X and have question about best use of drives for performance / storage utilization.

(hoping to set this up correctly from the start rather than trying to move things several months in)

My System: 

    MBP (late 2015) with 1T internal SSD drive

    External Drive 1:  8T RAID (thunderbolt, 400mb/sec)

    External Drives 2 and 3:  pair of 3T USB3 (connectect via thunderbolt doc, 150mb/sec)

Current plan:

    Internal SSD drive:  application only

    8T RAID:  Imported camera footage & FCP libraries (this will be my production disk)

    first 3T external / 2 partitions:  Time Machine (system disk only) and manual backup of current working files at end of each session ~ this drive stays  connected

    second 3T external:  Redundant backup of current working files at end of each session ~ this drive is disconnected except to backup

     (NOTE:  the manual backups will capture current camera stock and working FCP libraries)

My plan is based on a lot of reading and very little experience (much to learn!  Would you recommend a different disk strategy?  I have the option of adding storage / drives if there is a better way to handle workflow.

Thanks for any guidance!