I do not know why but I first thought the shade you encounter in the first area was sent by Groettsch to spy on you. Furthermore, I have no idea who have sent the roamer in the first area. If there is no explanation, then it's probably just a rogue creation that has wandered off.
Yes, I believe in previous games they were only refered to as "outsiders".
Yes, I remember in the previous games, Geneforge 1, 2 and 3, or at least one of those, it was mentioned that Terrestia was the second continent the Shapers have conquered. It was so long ago since I've played the first 3 games that I might no longer remember the exact details or wording. However, in the following games this continent was never mentioned again. I remember thinking back then that the rebels did not stand a chance against the Shapers. Can you imagine whole another continent full of them?
I've just finished playing Geneforge 1: Mutagen again and the player character does indeed land in Poryphra. Poryphra is a city on the northern coast of eastern Terrestia (GF4). This city is fifty miles (80 km) off from Sucia Island. The player character left from the eastern docks and must have sailed south to reach Poryphra. At least I believe so, because in the tombs on southern Sucia Island (the Shaper Tomb where you can find a servile playing his lute underground), you get a text stating that if you look hard enough to the south you can see the mainland (Terrestia). The Sholai came from the west; Western Sea (which for them would be the Eastern Sea). As they were approaching Terrestia a huge storm forced them to land on Sucia Island. It must have been a storm of continental proportions if they landed on Sucia Island while they were approaching from the Western Sea. They've sailed past the Nodye Coast, the Whitespires, Okavano Fen and maybe even Burwood Province because of this storm to reach Sucia Island. As Sucia Island must be located somewhere north of North Eastern Terrestia. The Sholai landed on the Eastern Docks of Sucia Island because of this storm. And I believe one of them said "they could see Terrestia" as the were approaching from the Western Sea but they landed on the Eastern Docks of Sucia Island because of the storm. I still find it very confusing if not inconsistent. I wish there was a huge map where we can see where the different landmasses are actually located. Then it would be easier to imagine what has actually happen.
Furthermore, for the shapers to have completely settled in western Terrestia first, coming from the direction of Sucia Island, then they must have sailed past Burwood Province, the Okavano Fen and the Whitespires to land on the Nodye Coast (the first province settled by the Shapers). Unlikely if you can see the outline of Terrestia south of Sucia Island. An explanation could be that they've landed in Burwood Province and kept it pushing west till they've reached the Nodye Coast. I think that is improbable.
I do not like these inconsistencies as it breaks the immersion of the game. I've always loved fantasy world geography.