It is not obvious from the datasheet for those servos if they will outright work at 5V since the only voltage specifications reported are the nominal operating voltages of 6V and 7.4V. However, I tested one from my office and was able to control it down to voltages of around 4V. So, I do not expect 5V to be an issue.
I am not very familiar with the PLC you plan on using, but in general, you should be aware that the signal that hobby RC servos use, which is oftentimes referred to as a PWM signal, might not be the same as the Power PWM Output on your PLC (which, judging by its name and description, looks like it is more appropriate for directly supplying power to motors and not sending control signals to a servo). You can learn more about the hobby servo signal (and how it is different from a PWM signal that changes its duty cycle) in this blog post.
Also, if your servos are able to move fast enough for your application by themselves when controlled from something like a hobby RC transmitter/receiver, but not when controlled from a Maestro, I suspect there is an issue with how you are using the Maestro. I could help you troubleshoot that if you tell me more about your setup. In particular, how fast were you updating your servo signals? What voltage were you supplying to your servos and what are you using to supply power? It would also help if you posted your Maestro settings file. To generate that text file from the Maestro Control Center, click
Save settings file... .