With BE, you have no controlled on your seat assignment, and while you can get assigned E+, it is not guaranteed. While status does override some of the onerous aspects of BE including allowing elite bag allowance, it does not override the seat assignment restrictions.

The Economy sections is split into 3 subsections. All three use the same non-BE ticket type / fare basis.

Regular Economy is the back 1/3 of the economy cabin and there are no seat selection fees.

Preferred Economy is the middle 1/3 of the cabin and no difference in seat / service from the rear section. There is an advance seat selection / access fee for non-elites / non-corporate preferred customers and at check-in the seat access fee is dropped -- open for section by any non-BE economy ticket. The logic of Preferred Seats is to save space for elites and certain preferred corporate customers and not have the seatmap fill up too earlier.

E+ is the front section and while the same seat, there is additional legspace. E+ is free access for all Gold and higher at booking and for Silver at check-in. There is a fee for all others except at the gate, GA can assign any seat for free, even BE.