From a UX perspective, when should you send the confirm your email message

In our sign up process, we ask the user to create a login (username and password) and then ask them to fill out the rest of their account which is a much longer process. There can be a one to many relationship between a login and these accounts (similar to your online banking where you have one login and through that one login you can access your savings account, checking account, money market account, etc). Before any of these accounts can be reviewed by our internal team and approved, we need to verify the user's email address.

The way I see it we have two options and I'm struggling to fund much evidence of which one is the better path:

1) we require the user to confirm their email before they can start the rest of the account creation process. i.e. I sign up with my name, email, and password and I then can't continue until my email is verified.

This seems like a cleaner option and we can assume in the approval process that the email is always verified. It would also let the user catch email errors earlier as they would have to validate the email address earlier. It would also alleviate issues with forgotten passwords. This way, a user can't go halfway through the rest of the process which is much longer, come back to it later, try to recover their password, and realize that the email is wrong and they have to start all over again.

However, we're concerned about the drop off. We don't want to create a flow where users abandon the process before even getting to the rest of the account set up because we make them confirm their email address.

2) we require the user to confirm their email address when they finish the whole account creation process. i.e. I sign up with my name, email, password, then I go through the long wizard to finish the set up and only at the end am I asked to verify my email.

It seems the main advantage here is reducing friction in the beginning of the process. We won't have users drop off because it takes to long to get the confirmation email or because they don't want to confirm it because they won't have to until the whole thing is done. In theory if they've gone through the effort of going through the entire set up process they're more invested and more likely to confirm their email.

The downside seems to be that users might enter a wrong email and then if they forget their password, they won't be able to recover it via email and resume from where they left off. They'd have to go through the whole process all over again.

Doing the second option has a few more technical implications than the first but it's definitely not a big issue. So the question is, from the UX perspective, which option would have more people convert through the whole process?

I have a feeling this has been contemplated by a lot of people already...I'm hoping someone with more resources than I have done some A/B testing on the issue.