Have you looked that flight up on Manage My Booking, you just need the 6 character booking code and your surname and it will show you the itinerary including the booking class.
The seats you mention are exit row seats which everyone has to pay for, no matter the booking class (it might be that they are free for Platinum members but even that I am not sure of). 46A is indeed a free window twin seat (as are 48 and 49K). Those have no extra legroom so the only advantage is that you only have (potentially) step over one extra person and as they are in the back it is debatable if that is worth the extra money.
That flight is currently very open for bookings (all economy fares are still for sale), so there may eventually be triple or even quadruple seats free when you get on the plane and you can travel ‘poor man’s business class).
Of course lots can change in 2 weeks, but if it was me (and my money) I would not yet pay to reserve an expensive exit row seat.