There are many goals to optimize when it comes to building cities and it is impossible to optimize all of them at the same time; some come at the expense of others.
1. Build as many cities as possible
2. Build cities as quickly as possible
3. Have max number of tiles available in a city (no overlap)
4. Use all available land and as much available water as possible.
Goals 1, 2, and 4 work well together and are the essence of ICS strategy.
Achieving goal 3 detracts from all the others.
It has been shown that ICS beats other strategies most of the time.
Many, myself included, do not enjoy it and rather build big magnificent cities.
Recently, I have been experimenting with the idea of having a mix of both kinds.
Some cities take advantage of all the tiles and are grown to mega cities; while others, from start, are destined to be minor cities. The Early landing strategy advocates a version of this idea as well.