The PE seats are open as they're just deemed "preferred" seats on domestic flights. I had this same thing on the 777HD YVR-YYZ.

I'd take anything in row 13/14 of "pe" as long as it's not a middle. Row 12 has the TV and trays in the armrests, I personally hate that. I love on the most of the fleet that the AVOD screen is stuck to the bulkhead or seat in front of you.

Oh btw, in PE (at least on the 777) there's basically no room under the seat. They give you a footrest (which...I'd prefer not to have, but it can be comfortable) but there's electronics under there as well and everything seemed to be misaligned, as if it COULD fit had they reconfigured a bit, but they want you to use that footrest. There's room for a purse, MAYBE a small backpack, but you're not fitting much else under there.

When do these 789s come into service?