Map size is the prime determinant for my build strategy. On smaller maps, I go for a denser build with significant overlap since everything happens earlier, resources are denser, and most expansion will be through conquest, not settlers. On the very large to fully expanded maps that I prefer, my strategy is very different. Some cities may overlap a few tiles but I have many more unused tiles than overlapped. There are a lot of reasons for this:
- for any given resource appearance frequency, the actual density decreases as map size increases so that one needs a big empire to ensure the strategic and luxury resources necessary to win. For example, even with coal turned up to 300 (the max) in the editor, I did not have any coal in my current game until my 92nd city. A resource only needs to be in one's cultural range, not city range to be usable so big empires with lots of gaps to be filled by culture later.
- you have much longer to expand peacefully and many fewer opportunities for early expansion through conquest. I tend to expand as quickly as possible to where I suspect/hope my borders will be and backfill later. I build these cities on good spots which inevitably means overlaps or more generally gaps.
- on very big maps, one will hit the hard coded city limit before all available terrain is settled. Therefore packing your cities tight just leaves more empty space and resources that can only be used through the very vulnerable colony and external road approach. I prefer the key resources in my empire, not vulnerable in case of war.
- I tend to build around the lower value tiles (deserts/jungle/) hoping to 'surround' them and gain the resources which appear later in the game through cultural expansion. Hard to surround tundra, but the approach is the same. I will build right beside a jungle because eventually those jungle tiles will be cleared but I try not to build right beside desert because that city will always suck.
I also tend to build two types of cities. The first are the cities on a river with lots of hills, mountains and grassland - high growth, high production - the engines of my empire's economy. I minimize overlap here but also hate to waste a good river tile so some compromises are required. Other cities are the settler/worker cities or just filler cities. Small maps, lots of overlap; huge+ maps, lots of gaps.
Bottom line, there are really no absolutes here. Fit your approach to map size, starting position, distance from other empires, resource appearance, your playing style, etc.