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The first point in the generated polygon is the location returned by GetLocation when used on the object. This also appears to be the "encounters default location" when trying to find a space to spawn creatures (if it fails it just uses this spot).
You can copy and paste placed encounters (which copy any edits made); blueprints then can update every instance of them by selecting Update Instances under Advanced.
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The spawn points govern where things spawn and the furthest one from the triggering creature is chosen. If none exist the game will try to spawn creatures out of visible range. Expect very barmy results if this is used !since "out of visible range" usually means "behind the player".
A note on the GFF says: "The SpawnPointList is only saved out if the encounter has spawnpoints defined for it in the toolset.Spawn points define a set of locations at which the game may spawn in creatures belonging to the Encounter. If an Encounter has no defined spawnpoints, then the game will try to spawn creatures out of visible range of the creatures that fired the Encounter."
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