A: Yes! Software RAID will work with any disk controller (IDE or SCSI) and any disks. The disks do not have to be identical, nor do the controllers. For example, a RAID mirror can be created with one half the mirror being a SCSI disk, and the other an IDE disk. The disks do not even have to be the same size. There are no restrictions on the mixing & matching of disks and controllers. This is because Software RAID works with disk partitions, not with the raw disks themselves. The only recommendation is that for RAID levels 1 and 5, the disk partitions that are used as part of the same set be the same size. If the partitions used to make up the RAID 1 or 5 array are not the same size, then the excess space in the larger partitions is wasted (not used).
A: The Mylex/BusLogic FlashPoint boards with RAIDPlus are actually software RAID, not hardware RAID at all. RAIDPlus is only supported on Windows 95 and Windows NT, not on Netware or any of the Unix platforms. Aside from booting and configuration, the RAID support is actually in the OS drivers. While in theory Linux support for RAIDPlus is possible, the implementation of RAID-0/1/4/5 in the Linux kernel is much more flexible and should have superior performance, so there's little reason to support RAIDPlus directly.