[M.Brane]

Personally I wouldn't use the partitioning setup you have if the Mac will be used as DAW exclusively. No real need, and if a drive fails the partitioning won't really help you any. Those drives are likely faster than the Mac's ATA bus so partitioning for speed won't gain you much if anything. If you really want to make sure the storage system is not a bottleneck (running both system, and audio drives on the same ATA bus certainly is not optimal) think about an inexpensive PCI host card.

As far as setting it up if you're 100% sure you the Mac is for PTLE only then do a basic OS install+ update, restart with the base extension set, install PTLE, set preferences according to the setup guide, and you should be good to go. Run DFA (Disk First Aid), and backup on a regular basis. If you can find an OS9 version of DiskWarrior that is an excellent utility to have on hand. Tech Tool Pro is good too. Whatever you do don't use Norton Utilities.