E-mail migration between servers without knowing accounts password

Hello!
All the e-mail migration guides found on Internet states the following migration guidelines:
1) Create email accounts with the same passwords as it was on old server;
2) Copy the mail directory content for user to the new mail server.

I just verified that if I:

1) delete some mailbox from server;
2) recreate deleted account with different password;
3) restore old account mail items backups to recreated account's directory.
The mail items is seen by user which is logged on with new password.

Questions:
Q1. Is this requirement that passwords must be the same? Is such migration plan is correct?

1) Create email accounts;
2) Send the new passwords to users;
2) Copy the mail directory content for user from the old to the new mail server.

Q2. Can I use the procedure above if I migrate email data between various Cpanel users. For example: Old server's account name is 'acc1', but the new server's account name is 'acc2' (full e-mail address remains the same)?