The importance of Find My...
If you have owned Apple devices over the years, registering the devices with Apple is always important. Apple isn't the only company that requires devices to be registered. Your Android, Google, and Microsoft devices and applications have the same requirements as well.
What Apple does want to know is what devices you own or have with you. There was a time when you were limited to the amount of devices you had on your account when using ITunes. These restrictions have went away over time but removing devices you don't own hasn't.
Updating your information with Apple can make it easier to sell devices, get devices serviced, or give them to friends or family when you need to.
The importance of two step verification
Two step verification is great to use if your phone gets into the wrong hands if it is setup properly.
In the case of Iphones, the proper way to setup two step verifcation is to have the verfication sent over to a secondary device (in case your phone isn't working as well).
This can be setup through the settings of your phone using current IOS settings. If you don't see the options in your settings, you should update it.