Hello Windscreen,
My youtube video is showing ~90IPM. I will post another video with max IPM ~145 I can achieve using these servos. yes servos are 730 for Z axis and 1090 RPMs for X and Y.
I didn't use any brakes, never had any issue Z axis falling down whether servo is on or off.
I used original bearings from Optimum, I believe those are AC bearings.
Let me know if you have any more questions.