Phone calls
Calls on my iPad not ringing on my iPhone X. If I answer the call on my iPad I can’t pick it up on my phone.
This would be because if you're using your iPad, it's dominant, and if you answer the call on your iPad, you can't then move over to your phone to continue the conversation. So, decide where you want to answer the call and answer it there. This is expected behavior.
I have no desire to make or receive calls on my iPad. I always have my iPhone with me. I have call forwarding to iPad turned off.