I used a 200x200 once, but it is not a good size, IF you want to play AW on a pan. You risk getting too many civs coming at once. It should be better than 250x250 for non AW.
512 limit is very useful for AW players as it helps slow down those Emp/DG civs a bit.
Yeah I left out the OCN, but it is not as important as the CF. Culture, it depends as I have played a number of 250x250 AWE and not had an issue with culture at 100K. If it defaulted to huge's 160K, that would be ok.