Which controller board is best for hooking up rasberry pi to Traxxas 5675 Titan 77?
Not without a controller
Not without a controller
Best is subjective
Many things
No


Yes, a controller is needed not only for precision speed control, but also current sourcing. Much to my surprise, these were NOT BLDC motors, they are brushed DC.

You need an ESC -- traxxas sells these as well. Ask them which is most appropriate for your motor.
This might work.