First, if I boot my iMac/i7 in 64-bit mode will Parallels work? I have read there were kext issues. if I leave MacOSX in 32-bit mode will it run 64-bit Linux or W7 systems or am I best sticking with 32-bit systems?
While the Parallels app is 32 bit, it runs Win7 64 bit quite well. There also are no issues with running Parallels on a 64 bit Snow Leopard (which is the default). You can use Win 7 64 bit or Win 7 32 bit, there is no difference at all - except for the limits of Win7 32 bit.