Some reported that powering the 5V to Vcc could damage the voltage regulator in some rare cases. But it is valid to do so. It's not a problem.
But using the servos on the other Vcc, I don't like that. The current and servo noise is going through the pcb of the Arduino Mini. The circuit board is not designed for that. On the other hand, it is just a small servo motor. So if it is only for testing, it will work.