I believe it does depend on the adapter, specifically what
ATA/IDE transfer modes it supports.
I'm fairly certain that all of the PCI architecture Macs that used IDE support drives up to PIO4 16.7MB/s with the B&W G3 adding UDMA 2 ("UDMA/33") 33.3MB/s and G4's eventually supporting even faster modes.
But the adapters sometime don't support the oldest/slowest transfer modes. I used this model adapter, which does PIO4 16.7MB/s and up:
It works just fine in my Performa 6360/PB3400 but no dice in my Quadra 630/PB1400 which only support up to PIO 2 8.3MB/s. Use compact flash in those.