How could I change webform submission tags to common html email tags?
I think you want HTML format template option to send an email with HTML format.

For this, you can use  htmlmail and mailsystem module and enable it and select "HTMLMailSystem" option at admin/config/system/mailsystem.

Now check step 3 at admin/config/system/htmlmail and select "Full HTML".

Now you can config you webform mail setting and select custom mail template and add your HTML tags and inline CSS in div.