As a Plat FF member you can request to have an exit row seat pre-allocated if it is available. Some really like these. But be aware that it can get noisy there and congested as people wait for the loo or use the exit row space to stretch and be vertical for a period.
Also note that the window seats on exit rows are slightly obstructed by the escape slide storage in the door.
Exit row and bulkhead seats are slightly narrower than standard economy seats due to the tray table and IFE screen fitting into the arm rest. That also means the arm rests cannot be raised between the seats.
My personal preference (if I have to be in WHY) is the bulkhead. But I am not overly tall and find the leg room between the seat and the wall to be ok. Taller people may find it insufficient. I would be ok with a C or H exit row seat, but probably would avoid the AB and JK exit row seats.
I always seek an aisle seat in the centre block of seats (D or G seat). I really don't like have to climb out over someone else or to have someone else climb out over me.
These are just my personal thoughts, and I know other people have differing views and experience.