I'd really appreciate the advice of someone who's experienced this particular seating layout!

I'm flying LHR-BOS (and return) on 623 and 624 respectively, which as far as I know is the 767-300 L. My "choose your seat" pages are throwing up a layout in Y with the C, D and E seats alone in row 16 and EC up to row 21, however the corresponding Seat Guru map shows something different, with F and G seats alone in the first row of EC.

I'm therefore having a little trouble trying to pick the best seat in EC for my flight- can anyone with a little experience with this point out any seats without windows, where the fuselage sticks out on recline or any other little negatives? Also- advice on the best seat to view the overhead screens would be great at the moment one of the window seats in row 18 is looking like my best bet...