Mail sent from a generated site usually comes from a no-reply address at a domain the recipient does not recognise, which is a good way to end up in spam.
Connect Gmail over SMTP and it comes from your own address, from a domain that already has a reputation.
This uses an app password over SMTP rather than the gmail.send OAuth scope, and that is a deliberate choice: gmail.send is a restricted scope requiring an independent third-party security assessment. Months of process for something SMTP does today.
An app password is also narrower. It can send; it cannot read your inbox or reach Drive.
myaccount.google.com/apppasswords, with 2-step verification enabled.
No. An app password for SMTP can send and nothing else.
Yes. Connectors are part of the plan; there is no separate integration fee.
At any time, from the same panel. The credential is deleted at the broker.