Magento 2 : How to Change Category Page Layout for Specific Category Only?

Step 1: First you need to add the following file.

appdesignfrontendMagemonkeysCustomthemeMagento_Cataloglayoutcatalog_category_view_id_{{id}}.xml

NOTE: Here you need to replace {{id}} with real category id

Now add the below code,

<?xml version="1.0"?>
<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" layout="2columns-left" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
    <body>
        <referenceContainer name="columns.top">
            <container name="category.view.container" htmlTag="div" htmlClass="category-view" after="-">
                <block class="MagentoCatalogBlockCategoryView" name="category.image" template="Magento_Catalog::category/image.phtml">
                    <arguments>
                        <argument name="image" xsi:type="object">MagentoCatalogViewModelCategoryImage</argument>
                        <argument name="output" xsi:type="object">MagentoCatalogViewModelCategoryOutput</argument>
                    </arguments>
                </block>
                <block class="MagentoCatalogBlockCategoryView" name="category.description" template="Magento_Catalog::category/description.phtml"/>
                <block class="MagentoCatalogBlockCategoryView" name="category.cms" template="Magento_Catalog::category/cms.phtml"/>
            </container>
        </referenceContainer>
        <referenceContainer name="content">
            <block class="MagentoCatalogBlockCategoryView" name="category.products" template="Magento_Catalog::category/products.phtml">
                <block class="MagentoCatalogBlockProductListProduct" name="category.products.list" as="product_list" template="Magento_Catalog::product/customlist.phtml">  <!-- Here you need to add your custom list file -->
                    <container name="category.product.list.additional" as="additional" />
                    <block class="MagentoFrameworkViewElementRendererList" name="category.product.type.details.renderers" as="details.renderers">
                        <block class="MagentoFrameworkViewElementTemplate" name="category.product.type.details.renderers.default" as="default"/>
                    </block>
                    <block class="MagentoCatalogBlockProductProductListItemContainer" name="category.product.addto" as="addto">
                        <block class="MagentoCatalogBlockProductProductListItemAddToCompare"
                               name="category.product.addto.compare" as="compare"
                               template="Magento_Catalog::product/list/addto/compare.phtml"/>
                    </block>
                    <block class="MagentoCatalogBlockProductProductListToolbar" name="product_list_toolbar" template="Magento_Catalog::product/list/toolbar.phtml">
                        <block class="MagentoThemeBlockHtmlPager" name="product_list_toolbar_pager"/>
                    </block>
                    <action method="setToolbarBlockName">
                        <argument name="name" xsi:type="string">product_list_toolbar</argument>
                    </action>
                </block>
            </block>
            <block class="MagentoCookieBlockRequireCookie" name="require-cookie" template="Magento_Cookie::require_cookie.phtml">
                <arguments>
                    <argument name="triggers" xsi:type="array">
                        <item name="compareProductLink" xsi:type="string">.action.tocompare</item>
                    </argument>
                </arguments>
            </block>
        </referenceContainer>
        <referenceBlock name="page.main.title">
            <arguments>
                <argument name="id" xsi:type="string">page-title-heading</argument>
                <argument name="add_base_attribute_aria" xsi:type="string">page-title-heading toolbar-amount</argument>
            </arguments>
            <block class="MagentoCatalogBlockCategoryRssLink" name="rss.link" template="Magento_Catalog::category/rss.phtml"/>
        </referenceBlock>
    </body>
</page>

Step 2: Now you need to add the following file.

appdesignfrontendMagemonkeysCustomthemeMagento_Catalogtemplatesproduct customlist.phtml

Note: Now you can add your custom code or design in this file for your custom product list for a specific category. Hope that helps.