Crashmon, regarding 3rd city it's like chess, I think. There is no
best move. Every option has pros and cons. You'll have to make a decision and stick to it.
A quick summary:
- you settle the copper (+2

+3

) and could
immediately start building an axe by chopping. You can further grow on two farms and work the stone netting +3

+7

at size 3 as sampsa pointed out.
Disadvantage, sharing the corn if off once and for all, although you could build an east city sharing the pig with London.
- you could settle 1NE of the copper, improve the copper (no road needed to connect - krikav), build two farms and finally improve the stone, netting +1

+11

at size 4 as Fippy pointed out. With AH and pigs pastured, you can grow on the corn in between.
Disadvantages a) you loose several turns b) pasturing the pigs has a higher priority c) when the copper is improved you cannot grow on it as long as 3rd city is size 1.
- I think settling 1N is off, because it kills a farm for further growing - but this is just my personal opinion. By killing the second farm you
must work the corn with 3rd city
or you are crippled to size 2
or you just connect the copper but don't work it, what would kill a +6

tile.
Just an idea regarding York: Is it reasonable to grow on a farmed floodplain while cottaging the 2nd one? Later, the farm could be turned into a cottage.