Greyhounds are amazing dogs, they are incredibly fit, and active but are perfectly happy to sleep through most of the day. I think you'd find it hard to find any dog that would be ok being left alone for more than 3-4 hours, have you considered getting 2? I dont know your circumstances, but if you can afford it, you wouldnt really be putting much more effort in, and then they can keep each other company throughout the time you're not there. Also, i know we hear it all the time, but please rehome a dog, not only do you save money, but its pretty self explanatory how amazing it is to give a dog a second chance. Ps. worked at a vets for 2 years

just incase thats any sort of reassurance of info
Oh and as for three of your choices, border collies and any type of husky require a lot of attention almost all of the time due to how intelligent they are. And a german shepherd might not be the best choice, whilst they're great for the first 7-9 years they will almost certainly develop a disease, they are the worst breed of dog for getting ill. It is just unlucky for them but as i was told at uni, if you dont know an answer to a question about a specific disease, just answer german shepherd. >.<