I bought an immaculate used Mac Pro and have a few questions on what to do regarding the drives. Its EFI is 64 bit so I can boot either 32 or 64.

What I currently have:
Burly for my backup drives
an external (eSATA) drive.
A 2 TB with 5 partitions (one containing Tiger plus apps; and the others for various storage subjects),
1 TB with 2 partitions (Leopard and 1 partition for doc storage).

What I do / my needs:
graphics and websites: which needs scratch disk for Photoshop and client doc storage
music production: which needs disk for recording audio and a disk to stream sample data* that is installed with the virtual instruments (750 GB)

* This disk I could either keep as eSATA or move it into the new mac.

The Mac Pro:
has a 120 GB SSD w/ Mountain Lion installed.
has another 1 TB drive

If I'm going to use ML at all, it might be good for internet because of security updates, etc. Had read about some problems with ML but maybe it's OK for apps too? And/or maybe ML should be reserved for 64-bit stuff?

I thought Snow Leopard for my main OS (the most solid?), but perhaps have a drive or partition for Leopard in case some apps (CS3, perhaps?) will do better than on Snow.

1) What usage would be the best to put to use for the SSD? OS, apps, docs?
2) SSD: put an OS on each partition?
3) Should I have the apps confined to each OS's app folder, or combine them into one place or partition? (most will probably be able to run on 10.5 or 10.6 as they are either UB or Intel only). I've read on Ricks trick but never implemented it yet.
4) I might want to have a small partition for Windows (for audio apps)
5) The whole 32 / 64-bit thing will be new to me so I didn't know whether apps should be divided / installed accordingly?
6) Is partitioning a good idea anymore?
7) eSATA card: I only need the 2-port but I see the one here only good for Snow? I have the single Burly. I saw the Newer Tech card that requires no driver and has no OS restriction. But it said it does not support Port Multiplier. My Burly is a 1-port connector, so it doesn't require port multiplier capability does it?

So I will have available:
two 1TB drives
750 sample drive (either move it into the computer or keep on eSATA)
a newer 2TB drive that is currently in my computer that I can move to the newer Mac (but will have to be reformatted to GUID).

I tried to make this clear so that it's not too much to read!

Thank you!