BuddyPress User Blog - Restrict for subscribers.

<?php
add_action( 'bp_setup_nav', 'bboss_maybe_sap_setup_nav', 90 );
function bboss_maybe_sap_setup_nav(){
    if( !class_exists( 'BuddyBoss_SAP_Blog' ) )
        return;

    $instance = BuddyBoss_SAP_Blog::instance();
    if( !user_can( bp_displayed_user_id(), 'edit_posts' ) ){//not an author
        remove_action( 'bp_setup_nav', array( $instance, 'sap_setup_nav' ), 100 );
    }
}

add_action( 'bp_setup_admin_bar', 'bboss_maybe_sap_setup_admin_bar', 70 );
function bboss_maybe_sap_setup_admin_bar(){
    if( !class_exists( 'BuddyBoss_SAP_Blog' ) || !is_user_logged_in() )
        return;

    $instance = BuddyBoss_SAP_Blog::instance();
    if( !user_can( bp_loggedin_user_id(), 'edit_posts' ) ){//not an author
        remove_action( 'bp_setup_admin_bar', array( $instance, 'sap_setup_admin_bar' ), 80 );
    }
}