Syncing iCloud Mail and Calendar from iPhone to iMac

Let's start with the iPhone. I have both the iCloud Calendar and Google Calendar on it, and they sync, so as long as I have internet or my iPhone, I can access my calendar.

Now let's go to the iMac. I use the web version of Google Calendar, and the pre-installed iCloud Calendar. But on the Mac, the iCloud calendar doesn't sync from iPhone to iMac, and the Google Calendar doesn't sync to iMac.

So I can't edit iCloud Calendar from Mac, but I can, when I have internet, use Google Calendar on Mac to then change the iCloud Calendar on iPhone, but I can't use Google Calendar on either iPhone or Web to change the iCloud Calendar on iMac.

Same issue with iCloud Mail, except it's with Gmail instead of Google Calendar

How do I just get them to all sync together?

Since I would say it's a MacOS issue, I'm tagging it Mac

Edit: I kinda solved it, but I don't know if I have to manually change the settings on every new Apple Device I purchase.