Hi,
Im around 6'4''tall and 4' wide so searching for the best eco seats is important for me as well. The exit seats are good from the point of view of legroom however if the seats next to you are occupied it is a little uncomfortable if you yourself are wide as well, particularly as the armrest goes all the way down to the horizontal part of the seat to incorporate the tray table. In a normal seat there is a little more room for the width of your legs to move as there is a neutral zone of a couple of inches under the armrest between your seat and your neighbours'. The 34" seat pitch in Y makes the normal seats more than adequate for me and I prefer them over the exit row if I can get seats next to me blocked.

The seats towards the back where the fuselage gets narrower do offer a little more room, however if the seat next to you is vacant the arm rest is not able to be folded back as far as a normal arm rest as the seats are really close together. There is however more lateral room if you have a window seat down back.

As far as requesting seats at check in, if you have no status you are not exactly likely to be given first choice unless you have incredible charm, personally know the check in staff, or the check in gal had a great time the previous night. From the point of view of staus, it has helped me immensely at check in to the extent that I have always been able to have seats next to me or even on either side blocked to make my journey more comfortable. Even in flight just after take off or just after doors are closed on departure, I have had crew come over to me (after I previously asked if there were any seats with more room available) and taken me to a seat which is more pleasurable.

Aisle seats c and H have a narrower space for legs due to the frame of the seat in front. This also hinders the space available for a small bag to be put under these seats.

Exit seats next to galley are the best as less traffic and better smell than those next to the bathrooms. Im not a cofffee drinker, but the smell of coffee from the galley at breakfast sure beats the one near the bathrooms towards the end of a long haul flight.

Finally, after much thinking and suffering in economy I have decided that J class discounted business is the way to go for me in the future. If all goes well with business and I am satisfied with the new ammenities at the new BKK airport for business class pax I will begin occupying the j seats on the flight to Copenhagen. F seats at J price are really a bargain but I will miss those cute FA's in economy. Oh well I will still be with them on the monthly Madrid run.
Cheers!