Yes, at the 3rd grade level, CTY is the same as EPGY. With the open enrollment (group or otherwise), you don't get the one-on-one support, but the online exercises are the same. (There are some options that require significant fiddling if you're in open enrollment, too - it's possible to automatically skip the math races, or to manually adjust the level / number of them, but it's not as easy as just asking someone to do it for you.)