Welcome to the community forums 😎
Buttonizer supports the Facebook chat widget for example, have you seen this knowledgebase topic about it yet? https://community.buttonizer.pro/knowledgebase/59-how-to-setup-the-facebook-messenger-chat-widget
I noticed that mail and whatsapp integrations send you to a different page.
On desktop the Whatsapp button links to the official WhatsApp API page, where people also are able to use the web variant of Whatsapp. On mobile devices it automatically opens the WhatsApp app, so it depend on the device you're using 🙂
Let me know if this helps! 🙂