Remove Customizer Control Choices (Type: Radio Array) using Child Themes

You can assign a new array there, with the updated options:

$wp_customize->get_control( 'your_control_id' )->choices = array( 'top' => 'top', 'bottom' => 'bottom' );

used this in my functions.php

function modify_choice( $wp_customize ){
    $wp_customize->get_control( 'your_control_id' )->choices = array( 'top' => 'top', 'bottom' => 'bottom' );
}

add_action( 'customize_register' , 'modify_choice',999 );