<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../lib/internal/Magento/Framework/Module/etc/module.xsd">
  <module name="Vendor_Module" schema_version="0.0.1" setup_version="0.0.1" active="true"/>
</config>

<?php

namespace VendorModuleSetup;

use MagentoEavSetupEavSetup;
use MagentoEavSetupEavSetupFactory;
use MagentoFrameworkSetupInstallDataInterface;
use MagentoFrameworkSetupModuleContextInterface;
use MagentoFrameworkSetupModuleDataSetupInterface;

class InstallData implements InstallDataInterface
{
  public function __construct(EavSetupFactory $eavSetupFactory)
  {
    $this->eavSetupFactory = $eavSetupFactory;
  }

  public function install(ModuleDataSetupInterface $setup, ModuleContextInterface $context)
  {

    $eavSetup = $this->eavSetupFactory->create(['setup' => $setup]);
    if (version_compare($context->getVersion(), '1.0.0') < 0){

      $objectManager = MagentoFrameworkAppObjectManager::getInstance();
      $customerSetup = $objectManager->create('VendorModuleSetupCustomerSetup');
      $customerSetup->installAttributes($customerSetup);
    }
  }
}

<?php

namespace VendorModuleSetup;

use MagentoEavModelConfig;
use MagentoEavModelEntitySetupContext;
use MagentoEavSetupEavSetup;
use MagentoFrameworkAppCacheInterface;
use MagentoFrameworkSetupModuleDataSetupInterface;
use MagentoEavModelResourceModelEntityAttributeGroupCollectionFactory;

class CustomerSetup extends EavSetup {

  protected $eavConfig;

  public function __construct(
    ModuleDataSetupInterface $setup,
    Context $context,
    CacheInterface $cache,
    CollectionFactory $attrGroupCollectionFactory,
    Config $eavConfig
  ) {
    $this->eavConfig = $eavConfig;
    parent :: __construct($setup, $context, $cache, $attrGroupCollectionFactory);
  }

  public function installAttributes($customerSetup) {
    $this->installCustomerAttributes($customerSetup);
    $this->installCustomerAddressAttributes($customerSetup);
  }

  public function installCustomerAttributes($customerSetup) {


    $customerSetup->addAttribute(MagentoCustomerModelCustomer::ENTITY,
    'branding',
    [
      'label' => 'Branding',
      'system' => 0,
      'position' => 100,
      'sort_order' =>100,
      'visible' =>  false,
      'note' => '',
      'is_used_in_grid' => true,
      'is_visible_in_grid' => true,
      'is_filterable_in_grid' => true,
      'is_searchable_in_grid' => true,

      'type' => 'int',
      'input' => 'boolean',
      'source' => 'MagentoEavModelEntityAttributeSourceBoolean',

    ]
  );

  $customerSetup->getEavConfig()->getAttribute('customer', 'branding')->setData('is_user_defined',0)->setData('is_required',0)->setData('default_value','0')->setData('used_in_forms', ['adminhtml_customer'])->save();



  $customerSetup->addAttribute(MagentoCustomerModelCustomer::ENTITY,
  'branding_type',
  [
    'label' => 'Branding Type',
    'system' => 0,
    'position' => 101,
    'sort_order' =>101,
    'visible' =>  false,
    'note' => '',
    'is_used_in_grid' => true,
    'is_visible_in_grid' => true,
    'is_filterable_in_grid' => true,
    'is_searchable_in_grid' => true,

    'type' => 'varchar',
    'input' => 'multiselect',
    'source' => 'VendorModuleModelEntityAttributeSourceOptions',
    'backend' => 'MagentoEavModelEntityAttributeBackendArrayBackend',
  ]
);

$customerSetup->getEavConfig()->getAttribute('customer', 'branding_type')->setData('is_user_defined',0)->setData('is_required',0)->setData('default_value','')->setData('used_in_forms', ['adminhtml_customer'])->save();


}

    public function installCustomerAddressAttributes($customerSetup) {

    }

    public function getEavConfig() {
      return $this -> eavConfig;
    }
}

<?php

namespace VendorModuleModelEntityAttributeSource;

use MagentoEavModelEntityAttributeSourceAbstractSource;

class Options extends AbstractSource
{
  public function getAllOptions()
  {
    return [
      'option1' => [
        'label' => 'Custom Model Numbers',
        'value' => 'custom_model_numbers'
      ],
      'option2' => [
        'label' => 'Camera Logo Stamp',
        'value' => 'camera_stamp'
      ],
      'option3' => [
        'label' => 'Camera GUI',
        'value' => 'camera_gui'
      ],
      'option4' => [
        'label' => 'Recorder Faceplate Decals',
        'value' => 'recorder_decals'
      ],
      'option5' => [
        'label' => 'Recorder GUI',
        'value' => 'recorder_gui'
      ],
      'option6' => [
        'label' => '2GIG Faceplate Stamp',
        'value' => '2gig_faceplate'
      ]
    ];
  }
}

$customerSetup->getEavConfig()->getAttribute('customer', 'branding')->setData('is_user_defined',0)->setData('is_required',0)->setData('default_value','0')->setData('used_in_forms', ['adminhtml_customer', 'customer_account_edit'])->save();

<?php

namespace VendorModuleSetup;

use MagentoEavModelConfig;
use MagentoEavModelEntitySetupContext;
use MagentoEavSetupEavSetup;
use MagentoFrameworkAppCacheInterface;
use MagentoFrameworkSetupModuleDataSetupInterface;
use MagentoEavModelResourceModelEntityAttributeGroupCollectionFactory;

class CustomerSetup extends EavSetup {

  protected $eavConfig;

  public function __construct(
    ModuleDataSetupInterface $setup,
    Context $context,
    CacheInterface $cache,
    CollectionFactory $attrGroupCollectionFactory,
    Config $eavConfig
  ) {
    $this->eavConfig = $eavConfig;
    parent :: __construct($setup, $context, $cache, $attrGroupCollectionFactory);
  }

  public function installAttributes($customerSetup) {
    $this->installCustomerAttributes($customerSetup);
    $this->installCustomerAddressAttributes($customerSetup);
  }

  public function installCustomerAttributes($customerSetup) {


    $customerSetup->addAttribute(MagentoCustomerModelCustomer::ENTITY,
    'branding',
    [
      'label' => 'Branding',
      'system' => 0,
      'position' => 100,
      'sort_order' =>100,
      'visible' =>  false,
      'note' => '',
      'is_used_in_grid' => true,
      'is_visible_in_grid' => true,
      'is_filterable_in_grid' => true,
      'is_searchable_in_grid' => true,

      'type' => 'int',
      'input' => 'boolean',
      'source' => 'MagentoEavModelEntityAttributeSourceBoolean',

    ]
  );

  $customerSetup->getEavConfig()->getAttribute('customer', 'branding')->setData('is_user_defined',0)->setData('is_required',0)->setData('default_value','0')->setData('used_in_forms', ['adminhtml_customer', 'customer_account_edit'])->save();



  $customerSetup->addAttribute(MagentoCustomerModelCustomer::ENTITY,
  'branding_type',
  [
    'label' => 'Branding Type',
    'system' => 0,
    'position' => 101,
    'sort_order' =>101,
    'visible' =>  false,
    'note' => '',
    'is_used_in_grid' => true,
    'is_visible_in_grid' => true,
    'is_filterable_in_grid' => true,
    'is_searchable_in_grid' => true,

    'type' => 'varchar',
    'input' => 'multiselect',
    'source' => 'VendorModuleModelEntityAttributeSourceOptions',
    'backend' => 'MagentoEavModelEntityAttributeBackendArrayBackend',
  ]
);

$customerSetup->getEavConfig()->getAttribute('customer', 'branding_type')->setData('is_user_defined',0)->setData('is_required',0)->setData('default_value','')->setData('used_in_forms', ['adminhtml_customer'])->save();


}

    public function installCustomerAddressAttributes($customerSetup) {

    }

    public function getEavConfig() {
      return $this -> eavConfig;
    }
}