Migration

I currently use UpdraftPlus and Updraft Central. I am trying to get a set in stone process of how to migrate a site to another domain using automated backups and the migration tool. This is what i have currently-

1. Install Updraft+ on new domain and login / update plugin.
2. Download backup files from Updraft Central / Google drive.
3. Upload backup files to updraft+ on new domain.
4. Restore the uploaded backup using migrator tool (using the “Restore and existing backup” option)

This has worked twice using manual backup files. However i have a few issues that i need to iron out.
1. To use automatic backups i need the database backup to be part of the backup containing the plugins uploads etc, but it is its own separate backup which has led to failed attempts at migration (all backup files on manual backup are part of the ‘same backup’)- Do the auto backups for database and files need to be taken at the same time for this to be achieved?

2. On my most recent attempt to solidify this process, i used a manual backup (like i have had previous success with). It succeeded, however my admin account no longer works to login, which is rather problematic. The only difference with this backup, was that I had checked the following options-

– Backup non-WordPress tables contained in the same database as WordPress
– WordPress core (including any additions to your WordPress root directory)

Any Help would be greatly appreciated!