Until recently, I was usually flying in Elite so don't have as much Y experience as Gus. I've now done 2 returns in Economy on LHR in the past couple of months and a few on regional flights. But in any case even in Elite I've made it my policy to walk round the plane. I have been on the 777s and 747s dozens of times and often looked closely at the Economy seating as Elite availability has become more of a problem. I fly through to Taipei and BKK-TPE is not so heavily loaded. I've used the chance to try different seats.

On the 777 row 45, the nearby toilet is for Elite and separated by a curtain. I don't think smells will be a problem and people in Economy shouldn't be queuing for it. (Although the policy isn't really enforced.) But if you're in C/H you are quite near to the flick of the curtain which could be annoying. In row 60, you are well separated from the toilet. In fact I forgot to mention, in row 60 you are by the galley where they leave some snacks out. Very handy!

On the 747, row 45 is right by the toilet, so smells could be a problem I suppose. 55 isn't near a toilet. Frankly the FAs seem to keep the toilets quite clean so I wouldn't worry. For me, extra leg room beats almost everything if you are in economy. I've yet to experience a smelly toilet on EVA, though usually the PL and Elite ones a more spacious and cleaner internally.

People do sometimes dwell in those exit areas - but there are better options at the back and that's where people sometimes gather for a chat. LHR-BKK is a nighttime flight - people usually sleep for most of it.

I can't see what the problem with 777 row 70 might be.