Be aware that digital servo's can create more force to hold position than equal analog servo's. And forgot to mention that high framerate systems can only work with digital servo's.
For a few years I am running Savox SC-1257TG servo's on my Mugen MRX4X, the 0.07sec@60degrees and 10kg force are enough. Before that I had KO wit 0.08sec and 8kg, both good servo's, if they work for 1/8 then the will do for sure 1/10.
Cheap high torque servo's are most of the times slow, that can give problems with taking corners. A populair servo amoung starters is the MG995 servo, stay away from it. Although it seems to be a good servo regarding the specs it is not precise and can have some difficulties finding position what will give a strange feeling to drive with.
Speed is only fiction but a 130+km/h MRS4 is for real.