There are a number of interlocking questions here, and the answer depends on exactly what you want to do. The short answer is yes, the more accurate answer is maybe.
a) You can do RAID 10 using the motherboard controller if it is supported in Linux, otherwise you need to do software RAID or a separate controller. WIndows is not compatible with mdadm (afaik) so you may require a hardware RAID card that is supported in both. If the motherboard is an AMD chipet you might consider a separate controller in any case as I hear that the RAID in some of the AMD chipsets is not the most reliable though that is entirely hearsay on my part.
b) As you can see, triple boot is possible. Adding encryption complicates it a little depending on whether you just want part of your drives encrypted or all of them (minus the boot partitions). If you use TrueCrypt for your windows encryption the volumes will be Linux readable. LUKS volumes should be Windows accessible via FreeOTFE. Note that TrueCrypt cannot do full drive encryption in Linux. LUKS cannot encrypt in place like TrueCrypt so installing it will wipe the current drive space. If you use EFS/Bitlocker for Windows encryption you will need a special utility to run in Wine to read the encrypted partitions (not always reliable)
c) If you use the SSD as the base drive for the array, the array will be limited by the size of the SSD.
The simplest route might be to install your favorite distro on your encrypted RAID array, and then install your secondary OSes on virtual machines.
