I believe it depends on the provider - in Italy there are three that currently support esims. A couple (Tim, Vodafone) let you rescan the qr-code multiple times with different phones. The third (Wind) provides a one time use qr-code, you need to show up at the shop and buy a new code (no idea if the serial is the same or not).

In every case you still need to wait for the qr-code to be posted at your mailbox (even if you can sign the contract online).