NFC card
NFC is not an app. The phone touches the card and the browser opens. QR is for phones without NFC.
What a tap does
The chip in a card, ring or bracelet hands over the profile address. Nothing is installed. iPhone and Android have read this for years.
The QR is written too
The QR on the back is the same address. No NFC, or showing it from a distance. After you edit the card both still go to the same number.
Before an event
Not on your own phone — on two strangers'. Cases and distance change the result.
Where it breaks
A chip on a metal table, a stale URL, testing only on your own phone. Those three cases produce no visits.