Use PFS3ds (Direct-SCSI). The other version of PFS needs TD64 which is not part of OS 3.9. The SCSI version even works without OS 3.9 (up to 8 GB).
what is the max speed that I should set the card to?
You cannot change speed. Are you talking about MaxTransfer? That's not speed, it's size. Yes, it's the same size as FFS. It's not dependent on file system but on hardware.