The XR is not an old phone (it was released in October 2018) - it has all of the security capabilities of the current iPhones.
As I have said a number of times if "find my iphone" is turned on (which it is by default these days) then you cannot use an iPhone without knowing either the pin code or the icloud password - resetting the device in the manner you linked will not get you in to a phone without the password. Please trust me on this - we have a number of iPhones that have been essentially bricked because the user when returning them didn't turn off find my iphone and we don't have access to their icloud account - Apple will not unlock the phone for us and so they cannot be used - even on fairly old versions of iOS and older devices this is the case.
EDIT : And as far as the SIM goes a large amount of call costs can be run up pretty quickly with a stolen SIM - and you may be liable for them right up to the point you inform the mobile company that it has been stolen.
Edited by ian72 (Fri 24-Jan-20 12:15:52)