I did a Universal Install of Mac OS 8.6 and I have two similar control panels. One is called PowerBook SCSI Disk Mode and the other is called PowerBook SCSI Setup. What's the difference?

Although the control panels have similar names, they have slightly different functions and should not both be used on the same model of PowerBook.

The PowerBook SCSI Disk Mode control panel should be used with any PowerBook model available before the PowerBook G3 Series (Bronze keyboard). It allows you to set the SCSI Disk Mode address on the PowerBook when you connect the PowerBook to another Macintosh as a SCSI disk drive.

The PowerBook SCSI Setup control panel should be used on the PowerBook G3 Series (Bronze keyboard). It allows for the same functionality but in addition it also offers the option to scan for and mount SCSI devices when coming out of sleep.