Specifically, am deciding between Settlers III, or Settlers II Anniversary, to play first.

Wondering if it may seem better to play the one first or the other, related to mechanics; if it's likely to be "spoiled on the mechanics" of the one vs the other. Does that make sense?

Settlers III is a bit of a PITA to get running. See, when it was added here, they never removed the serial key requirement, which while that can be found easily enough, there's other issues, such as the game running in glorious squint-o-vision, whereas Settlers II Aniv runs on actual graphical resolutions.

Do you mean III runs at a set resolution that cannot be changed, and things are too tiny, or too blurred? Is IV any better in that regard?

As far as mechanics, strategy elements like "roads or no roads" is the type of gameplay concept was wondering about (potentially detracting from the one or the other if played first).