How do I change the page the login form redirects to?

In your child theme's functions.php file add:

function gp_login_redirect( $gp_redirect ) {    
    $gp_redirect_link = '';    
    $gp_redirect = '<script data-cfasync="false" type="text/javascript">window.location.replace("' . $gp_redirect_link . '");</script>';    
    return $gp_redirect;
}
add_filter( 'gp_redirect_filter', 'gp_login_redirect', 10, 2 );

Where $gp_redirect contains the redirect link. So to redirect to your BuddyPress profile page use:

function gp_login_redirect( $gp_redirect, $gp_user_data ) {    
    $gp_redirect_link = bp_core_get_user_domain( $gp_user_data->ID );    
    $gp_redirect = '<script data-cfasync="false" type="text/javascript">window.location.replace("' . $gp_redirect_link . '");</script>';    
    return $gp_redirect;
}
add_filter( 'gp_redirect_filter', 'gp_login_redirect', 10, 2 );

For older versions of the theme use:

Open lib/inc/login-settings.php and find:

echo "<script data-cfasync='false' type='text/javascript'>window.location.reload();</script>";

Replace with:

$gp_redirect = '';
echo "<script data-cfasync='false' type='text/javascript'>window.location.replace( '" . $gp_redirect . "' );</script>";

Where $gp_redirect contains the redirect link. So to redirect to your BuddyPress profile page use:

$gp_redirect = bp_core_get_user_domain( $gp_user_data->ID );
echo "<script data-cfasync='false' type='text/javascript'>window.location.replace( '" . $gp_redirect . "');</script>";