I fully agree. It depends on your goals. There is no right or wrong way for everyone, just the way that is best for you.
1. Do I buy seperate Egg birds and meat birds.
There are advantages and disadvantages both ways. If you are buying all the feed, the specialized birds are much more efficient in converting that feed to meat or eggs. If they can forage for a lot of their food, that is not nearly as big an issue.
If you raise the broilers, you have to harvest them within a fairly short time window or they get medical problems. With dual purpose, you can spread the harvest out over a longer time. If you have regular power outages, do you want a lot of meat in your freezer?
If you raise the broilers you can cook them just like the ones you buy at the store. If you raise the dual purpose, you harvest them later and the meat will be a lot tougher and stringier if you cook them the same way. To me, it is a matter of the age you harvest them, not that the broilers are bred to be more tender. They don't age enough to get tough. I cook my dual purpose slower and in moisture. They get really tender. But I would never fry one.
If you go with the broilers, you have to buy chicks each time. They don't get old enough to breed and lay eggs. If you go with dual purpose, you can hatch your own eggs. One problem with this is that you will get half roosters and there is not a lot of meat on them. You can eat them anyway, people eat tiny quail. There is just not a lot of meat and if you are buying the feed, it becomes expensive meat per pound. And unless you choose your breeders carefully, over time you lose some of the benefit of them being specialized egg layers. With chicken genetics, unless you reinforce genetic traits each generation, you lose those traits.
There are plenty of other advantages and disadvantages each way. It just depends on your goals.
2. Do I go with a dual purpose breed like the Buff Orpingtons and if so when do you harvest them for meat?
You'll get different opinions on when to harvest Dual Purpose. Some of it might depend on how you feed them. If you keep them confined and feed them a meat bird diet, they will grow a lot faster than mine that get a regular diet and free range. I would never consider harvesting one before it is 15 weeks old, and usually wait until at least 18 weeks. I've read on here where some people harvest them at 12 weeks. I would not find enough meat on mine to make it worth the effort.
3. Do I buy started birds that are at the point of lay?
Pure personal preference. If you buy POL pullets, you know what you are getting, you get eggs pretty soon, and you don't need to brood them. If you are buying broilers, you already have the brooder and equipment, so that would not be a savings for you.
I'll mention disease. If you get your chicks from a reputable hatchery, the odds of bringing a disease into your flock are really tiny. If you bring in started pullets, those odds go up. I think the risk of them bringing a serious disease is blown way out of proportion in this forum, but when they do, the results are really catastrophic. It is a classic risk analysis problem. The odds are really low but the consequences can be really bad. Is the risk worth it to you? You can mitigate this risk a little by quarantining, but quarantine is not 100% effective. Some chickens get immunity easily at a young age to some diseases and will never show the effects themselves, but they can still infect other birds that don't have this immunity. Then you have the possibility that they can bring in a not serious disease, something that can easily be treated. The odds of this happening are higher, but the consequences are much less severe.
If you buy sexed chicks, you might get a rooster. You could eat him anyway so that may not be a big deal. And you can mitigate that by buying sex links.
Also I have 2 4'X2' coops with 8'x4' runs I was thinking of using these as tractors to run along the paths between my veggie garden. I was considering puting the meat birds in them so they got plenty of greens and insects while they grew. Any thoughts
Lots of people do that with broilers, egg layers, or dual purpose. I did something similar with dual purpose for a while. You have to be committed to moving them regularly. I just did not want to work that hard and you are tied down as far as vacations go but many people do.
Personally, I prefer the flavor of a dual purpose cockerel. I eat my extra roos, and they are much more flavorful and almost all dark meat compared to store bought chicken. But they have very flat breasts, the meat is tougher, and it costs a heck of a lot more in feed to grow them out to size. It's all in what your prefer, and your goals. 
