I agree with what a lot of people have said here, in so far that the best managers are those that can blend their managerial and engineering skills to benefit the project. Having someone who is great at the managing but cannot understand the technical part of the project is pointless as they wont be able to communicate the importance of the project. Having someone who understands all the technical aspects will be unable to put the project in the scope of benefit to the company. The best teams are merely an extension of this. Having a team with members that can both understand the technical aspects whilst also understanding the business and managerial aspects leads to better outcomes. The teams must also not be fully staffed with people who are perfect 50/50 splits of these abilities. The more technical people can complete the more technical aspects whilst the others can complete the non-technical aspects.

Teams are all about balance, so a good team successfully balances the strengths of its members. There is no magic ration, but it requires trial and error to get correct.