Torah V’Daas has many Roshei Yeshiva. R’ Belsky and R’ Reisman are two that immediately come to mind.
I’m not sure who is considered the “top” Rosh Yeshiva in the Mir now.
A yeshiva can have more than one “top” Rosh Yeshiva. Usually the one giving the highest shiur is considered the “top” RY. However, in some yeshivos, there may not be one shiur that is considered the highest. There may be 2 or 3 shiurim that are just in different topics or different styles that are all considered the highest shiurim.