My experience with these IDE-SATA adapters is pretty limited but certainly not great. Personally I'd recommend picking up a Molex-Dual SATA power adapters from eBay and then purchasing one of these SATA controller card | eBay
or the like. The last time I used one of these SATA controller cards it didn't actually work, I remember Vista hanging on the boot screen, but I just probably bought a bad card or just a cheap one.
With regards to whether you should use your SATA drive for booting, the whole idea is SATA is that it is faster than IDE, so yes, you want to use a SATA HDD as your boot drive if you can. I'm not sure what "type" the BIOS would give your hard drive if running off a controller card, I'd imagine it would be SATA configured as IDE or Enhanced IDE (depending on how old your motherboard is) but I wouldn't worry about such things really, the speed difference between having a SATA HDD set as IDE, SATA or AHCI is barely noticeable unless you are constantly writing to the hard disk, that sort of stuff is more important when it comes to SSDs.