Craft 5 introduced several general configuration changes that give you more control over your Craft installation.

Part of the accessibilityDefaults configuration array to control if search inputs should be focused on page load.
You can set the Utilities you don’t want to show in the control panel across all environments. The setting takes a string of comma-separated utility handles (find them in the URL slug; e.g. system-messages, deprecation-errors). You can also set this via an environment variable called CRAFT_DISABLED_UTILITIES.
return GeneralConfig::create()
//...
->disabledUtilities('system-messages, deprecation-error');
In your .env file:
CRAFT_DISABLED_UTILITIES=system-messages, deprecation-errors
Specify custom locale aliases that will be included when fetching locales. Should be defined as an array per GeneralConfig.php.
Supports the new partials rendering feature for elements (with the new longform content feature of CKEditor specifically in mind. The path can be anywhere within your project, but the default is _partials at the root of your templates directory. The partials template path will automatically have an element type handle included, e.g. _partials/entry/. You will need to create that subdirectory yourself.
return GeneralConfig::create()
//...
->partialTemplatesPath('_special/partials');
In your .env file:
CRAFT_PARTIAL_TEMPLATES_PATH=_special/partials
Set the handle that Craft should use for storing temporary file uploads. To set this per environment, you can use the CRAFT_TEMP_ASSET_UPLOAD_FS envrionment variable with the handle of the filesystem.
return GeneralConfig::create()
//...
->tempAssetUploadFs('tempFs');
In your .env file:
CRAFT_TEMP_ASSET_UPLOAD_FS=tempFs
When Craft looks up a template file on the front-end, it will now look for .twig templates before .html templates since the recommended extension is .twig.