When I first started with aerial imaging, I bought a gimbal that was plug and play with the NAZA M. Great for ease of use, but I soon learned that it was not so great for smoothness.
The gimbal was an Alware brand that was servo fired. Servos have gears. And no matter if they are digital or analog, they are just plain jittery and you can’t get rid of it no matter how hard you try.
The issue isn’t with the pitch angle so much as it is with the roll angle.
Brushless motors on the other hand don’t have gears and are silky smooth. The issue with BL gimbals however is finding one that doesn’t cost you your firstborn (ZenMus) and one that you can actually hook up to your computer and your radio and control its angles so that in flight or on the bench you can get it to point in the direction you want it to. Good luck with that.
You can buy a brushless (BL) gimbal in two axis or three axis, fully assembled with the motors, control board and sensor. or you can buy just the barebones with nothing. Or you can buy them with the motors and no control board. Regardless, it probably won’t come with any kind of decent instructions. So be prepared.
As this is a rapidly growing part of our hobby, you can expect this area of the hobby to become crowded with more and better choices sooner rather than later.
Good Luck Buy offers a ton of different gimbals at decent prices. Witespy sells the control boards. And more recently, HK is getting into it big time with Alex Moss boards and gimbals.