[Note to anyone reading this, only 90% sure I’ve got this right, so please feel free to contradict me 👍]
550 is the size, (the length of the can?)
Speed is usually indicated by its T number.
T stands for turns, or the number of times the wire is wrapped around the rotor.
Generally the lower the T the faster the motor will spin, but the less torque it produces.
From memory, standard ftx motor is a 15T, a reasonable compromise between speed and power.
By contrast, my crawler has a 35T motor, really slow, but will pull up the steepest slope from a standing start.
Never as simple as that as you can increase torque or speed by adjusting gearing within reason, and not all motors are made the same. Got to say, not madly impressed with the FTX one but at less than £8, can’t really complain.
I put a 21T sport tuned motor in mine, and it was just as fast as the 15T ftx one but with an extra bit of torque..... but at 3 times the price. 🤔