Choosing the best DC motor to use as a generator
If you are going to generate the 'most power possible', you need a motor that is large enough to absorb all the power the blades can generate, at the rotation rate of the turbine.
If you don't know the expected rate, and you don't know the expected power, then any motor will do, while you get doing some experiments. Make sure the motor is easy to change, as when you are disappointed by your first go, you'll want to change it to something bigger/better/different.
A permanent magnet motor is easiest to use, generating DC directly. A brushless motor will need a 3 phase rectifier, but will be more compact for any given power. Use schottkys rather than silicon diodes to make best use of the low voltage output.
Most motors tend to spin quite quickly to deliver their rated power, any practical sized turbine will spin way slower than those. So if you have a choice, choose a 'low speed' motor.  A wheel-hub motor intended for a powered bicycle might be a good match. You might be able to find a geared motor, though the gearbox will absorb some of your wind power.
At the low speeds involved, it might be practical and fun to make your own brushless generator, maybe integrated right into the turbine. There are several videos on youtube showing people making axial generators by gluing high strength magnets to flat steel plates.