In the T-FHSS mode you can choose for digital servo (333Hz) or analog servo (65Hz), in T-FHSS-SR mode you can choose between digital (333Hz) and SR mode (833Hz), not sure if the UR mode has such an option....

Basically normal digital servo's are rated up to 333Hz frame speed although Sanwa has a 384Hz (I believe) SHR mode that will work with most servo's. As you are a heli guy the 760usec servo's or also so called small band should be known to you. Problem is that most of them are rated up to 500Hz but there are 800Hz (and higher) to find out there. Only Futaba SR servo's can also be programmed with extra settings like moving speed, power and some other stuff. There are 3 or 4 different speed modes to choose in SR mode but basically those are presets you still can adjust to what you want. Dario Balestri made a short video about this.