No it was NEVER necessary, even with earlier OS's......
And there is NO optimum set-up, only one which suits YOUR needs....
If you still NEED OS 9 for classic mode, the logical uses for that 30gb drive would be 3-4GB for 9,and divide the rest between PS scratch disk and VM swap space, if you are so inclined.......and keep the 40gb for OS X
As for the ram, yes more is always better, for OS X especially. Apps like Photoshop & Toast will always run better with more, the other apps you listed wont show any difference. OS 9 can only use 1gb anyway
Whether or not it is worth it, really depends on your wallet
