Don't worry if the drive has a ATA/133 interface. It'll work fine on any ATA bus - assuming the ATA bus can recognize the full capacity of the drive (yours will). You should be OK with your ATA/100 interface and 200GB drives.
Some ATA/66 interfaces won't recognize disk capacities over 137GB. This won't be a problem for your ATA/100 interface.
It won't be a 'bottleneck', so to speak, if you use a ATA/133 hard disk on a ATA/100 interface. Almost no hard drives can saturate even a lowly ATA/33 bus.
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You
should be able to use pretty much ANY ATA (aka, IDE or EIDE) hard drive on your Mac. The only limitation is the disk size - and that's not a problem either, since your ATA/100 interface will support the largest disks currently available.