You will find the corresponding option inside:
Dashboard >> Reign Setting >> Community Settings >> BP Layout Management
Here you will find the following options:
Select Header Position: Allows you to select a header position. A user also has an option to edit the same, in that case, it will be overridden.
Select Member Header Layout: Allows you to select member header layout. A user also has an option to edit the same, in that case, it will be overridden.
Select Group Header Layout: Allows you to select a group header layout.
Select Member Directory Layout: Allows you to select member directory layout.
Select Group Directory Layout: Allows you to select a group directory layout.
BuddyPress Layout Management Settings: