We can do it by using preference if we need to add or edit some information in createPost controller.

To do that we will need a module : Magemonkeys_General

We have need two files.

Create di.xml file in this folder app/code/Magemonkeys/General/etc/

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <preference for="MagentoCustomerControllerAccountCreatePost" type="MagemonkeysGeneralControllerMagentoCustomerAccountCreatePost" />
</config>

Create CreatePost.php in this folder app/code/Magemonkeys/General/Controller/Magento/Customer/Account/

<?php

namespace MagemonkeysGeneralControllerMagentoCustomerAccount;
use MagentoCustomerApiCustomerRepositoryInterface as CustomerRepository;
use MagentoFrameworkAppActionHttpPostActionInterface as HttpPostActionInterface;
use MagentoCustomerModelAccountRedirect as AccountRedirect;
use MagentoCustomerApiDataAddressInterface;
use MagentoFrameworkApiDataObjectHelper;
use MagentoFrameworkAppActionContext;
use MagentoCustomerModelSession;
use MagentoFrameworkAppConfigScopeConfigInterface;
use MagentoFrameworkAppCsrfAwareActionInterface;
use MagentoFrameworkAppObjectManager;
use MagentoFrameworkAppRequestInvalidRequestException;
use MagentoFrameworkAppRequestInterface;
use MagentoFrameworkControllerResultRedirect;
use MagentoFrameworkExceptionLocalizedException;
use MagentoFrameworkPhrase;
use MagentoStoreModelStoreManagerInterface;
use MagentoCustomerApiAccountManagementInterface;
use MagentoCustomerHelperAddress;
use MagentoFrameworkUrlFactory;
use MagentoCustomerModelMetadataFormFactory;
use MagentoNewsletterModelSubscriberFactory;
use MagentoCustomerApiDataRegionInterfaceFactory;
use MagentoCustomerApiDataAddressInterfaceFactory;
use MagentoCustomerApiDataCustomerInterfaceFactory;
use MagentoCustomerModelUrl as CustomerUrl;
use MagentoCustomerModelRegistration;
use MagentoFrameworkEscaper;
use MagentoCustomerModelCustomerExtractor;
use MagentoFrameworkExceptionStateException;
use MagentoFrameworkExceptionInputException;
use MagentoFrameworkDataFormFormKeyValidator;
use MagentoCustomerControllerAbstractAccount;

class CreatePost extends MagentoCustomerControllerAccountCreatePost
{
	/**
     * @var Validator
     */
    private $formKeyValidator;
    protected $inlineTranslation;

    /**
     * @var MagentoFrameworkStdlibCookiePhpCookieManager
     */
    private $cookieMetadataManager;

    /**
     * @var MagentoFrameworkStdlibCookieCookieMetadataFactory
     */
    private $cookieMetadataFactory;

    public function __construct(
    	Context $context,
        Session $customerSession,
        ScopeConfigInterface $scopeConfig,
        StoreManagerInterface $storeManager,
        AccountManagementInterface $accountManagement,
        Address $addressHelper,
        UrlFactory $urlFactory,
        FormFactory $formFactory,
        SubscriberFactory $subscriberFactory,
        RegionInterfaceFactory $regionDataFactory,
        AddressInterfaceFactory $addressDataFactory,
        CustomerInterfaceFactory $customerDataFactory,
        CustomerUrl $customerUrl,
        Registration $registration,
        Escaper $escaper,
        CustomerExtractor $customerExtractor,
        DataObjectHelper $dataObjectHelper,
        AccountRedirect $accountRedirect,
        CustomerRepository $customerRepository,
        Validator $formKeyValidator = null
    ) {
    	$this->formKeyValidator = $formKeyValidator ?: ObjectManager::getInstance()->get(Validator::class);
        $this->accountRedirect = $accountRedirect;
    	return parent::__construct($context,$customerSession,$scopeConfig,$storeManager,$accountManagement,$addressHelper,$urlFactory,$formFactory,$subscriberFactory,$regionDataFactory,$addressDataFactory,$customerDataFactory,$customerUrl,$registration,$escaper,$customerExtractor,$dataObjectHelper,$accountRedirect,$customerRepository,$formKeyValidator);
    }

	public function execute()
    {          
        /** @var Redirect $resultRedirect */
        $resultRedirect = $this->resultRedirectFactory->create();
        if ($this->session->isLoggedIn() || !$this->registration->isAllowed()) {
            $resultRedirect->setPath('*/*/');
            return $resultRedirect;
        }

        // We can write our login here
    }
}

we will also need to add private function in this file as we used execute method.

/**
     * Retrieve cookie manager
     *
     * @deprecated 100.1.0
     * @return MagentoFrameworkStdlibCookiePhpCookieManager
     */
    private function getCookieManager()
    {
        if (!$this->cookieMetadataManager) {
            $this->cookieMetadataManager = ObjectManager::getInstance()->get(
                MagentoFrameworkStdlibCookiePhpCookieManager::class
            );
        }
        return $this->cookieMetadataManager;
    }

That’s it.