It varies. Basically overclocks arent based strictly upon the chip as a family, as much as they are based upon the pick of the litter that u got. I'd imagine you are getting towards your limit on your overclock. Is your second question mean will it do as well in framerate, or will it do as well in the overclock compared to the oc of a 5200?
-To give u some bearings, my gf3ti200 had a non-spinning fan that seemed to fail after 3 yrs of use. I managed to oc it to 206/481 WITHOUT the fan spinning. I think i just got lucky, but many people i know have gotten their ti200's above ti500 speeds. Just keep bumping by 2-3 mhz and thoroughly testing it at each point.