6.2 RC4 is a general de-bugger and doesn't change combat but does make the game more difficult by making the enemies stronger (not on the battlefield though, they just tend to be more aggressive and have larger armies and more alliances against you). However 6.2 doesn't create the Crusader States from Templars.
The
RR1.3/RC1.8/CBUR/BFTB/BGR IV Compilation does remove Templars and replace them with Crusader States but does make many changes to combat. However it's not a huge difference apart from some key areas with archer units. Generally spears, cavalry, heavy infantry all act pretty much the same, just better balanced. See the sub-mod thread for more info.