How to make game like the total war games?

How would I go about making it so that the camera is movable etc and the troops are selected in groups and cant be selected individually

1, make a custom character controller that controls only the character, and handles unit selection.

2, you need a hierarchy to your units, if you click on a unit, it should return the group it is part of and select all members of the same group.
you will need to define a variable that stores this, and have this available on all units.