They would be separate emails, but not sure anyone has gotten an email regarding previews. Regardless, it’s not necessary to get the email. I didn’t for SWGE and I could’ve booked it with a voucher. Not saying you can for sure, but it’s definitely possible.
It’s interesting, you can go back and search the question about vouchers being accepted for SWGE and post after post- Nope, can’t do it. Yet when they released the reservations, you could. lol