White Spektrum adds its own settings page under Appearance → Settings. It has three tabs.

General

Reading

• 404 Page: choose a page to show when someone visits a link that doesn’t exist. Set that page to Private so it doesn’t appear anywhere else on your site.

Clean ClassicPress

• Disable Emoji Scripts: all modern browsers support emoji, so this removes the extra JavaScript loaded on every page.
• Embeds: removes the JavaScript that allows other sites to embed your posts.

Themes

Shows information about White Spektrum.

Plugins

Recommends Regenerate Thumbnails, which regenerates all thumbnail sizes for images already in your Media Library. It’s handy after switching themes or changing the featured image size.