About M-84 MBT I think it is a second generation MBT based on Russian T-72 with some Yugoslavian new techs in 1982 (84), while The Type T-98 is a generation higher.
According to Chinese sourse M-84 is an excellent MBT but is only equivalent to Chinese T-85, while China already developed T-88, T-90, T-96, and now T-98, T-99 ,T-2000.
Here is a summary picture of M-84 MBT in Chinese:
And Chinese T-98 is surely one of the top MBT's in the world today.