OK [Takes deep breath]

7200rpm ATA drives will work, but you have two dual channel busses to use in total and one is faster than the other. ATA and IDE. Both look the same, and are backwards/forwards compatible, but like I say, one is faster. I'm guessing you plan on RAIDing the two faster drives, so you should stick these on the faster ATA bus. (Thats the one your current drive will be on at the moment, Optical drive will be on the IDE as standard).
This means that you may lose some general system snappiness and slow your boot time, since you will have to move your boot drive to the slower IDE bus. I think you should be OK to boot from the IDE bus with a slave drive. Best to use the Optical as master, as they tend not to be bootable otherwise.
Of course if you go with the SATA card and SATA drives (all three), then your data access and boot time and general snappiness will all be much faster. So get a bootable one. Some of them may not be.

As for optical drives, the most popular choice with modders is the Pioneer DVR-1XX Range most of these (from the 103 up to the 109, no doubt the 110 soon) have been fitted as standard in a Mac at some point. You can certainly flash them to be like an OEM Apple version without too much fuss. See the FAQ and drive compatability database at XLR8yourmac.com for more info. PC versions are cheap too.

As for noise, the G4s got noisier as they went on. Your sawtooth is an early G4 and will be virtually silent. Especially if you compare it to a Mirror Door.

As for the riser card, not entirely sure what you mean. If you mean a single card with 2 PCI and 1 AGP slot, I would tend to avoid such items. Simple is safer with this sort of thing. A single slot riser (should be available for PCI or AGP) should be nothing more than bunch of wires printed on a pcb. Just to extend your existing slot around a corner. If it has big, complicated looking chips on it too, it likely needs drivers. Which likely don't exist for the Mac.