I guess it might help to give you my thoughts on collie/greyhounds. Mine is 1/4 collie 3/4 greyhound. He's about 29" at the shoulder and 65#. He's a nice biddable dog and easy to keep. In the forest he sticks with me pretty well though he'll chase anything you put up. I had to use an e collar to break him off deer. But as he's gotten older I can pretty much call him off of anything.
He's fast and strong but he doesn't like getting bit. So, he's more useful for rabbits, possum's and the like.
Oh, and cold weather in not a problem for him. he can sleep out here in Michigan without any problems. He's about three years old in these pics.