I see, thanks for the write-up.It doesn't really matter. It doesn't really feel like a "Part 1". If it wasn't for a vague mention in the ending voiceover, it wouldn't have felt like a "Part 1" at all.
Obviously we don't quite know how Part 1 and 2 content will connect, and feasibly they could add sidequests to the Part 1 areas through Part 2, but as it is right now it felt really self-contained.
The expansion has very low-feeling stakes. You're helping a small fishing village to boost its economy by braving a dungeon to turn on a forge. I enjoyed it, but a lot of people complain that it didn't really feel tied into the main story or like it had an "epic" narrative of its own.
I like the new companions well enough, but one doesn't get a companion quest at all, and the other's companion quest is one of the shorter and more simple ones.
It's more Pillars, basically. A new town and a couple surrounding areas, new sidequests, and a new large dungeon that is pretty satisfying as far as large Pillars dungeons go. For hardcore types there's a new dragon to fight and a level 14 siege quest, but I poked at those and realized I just don't have the stuff for it. Whether that's "worth it" is up to the individual, I can definitely see people answering "no", but it was for me.
I'm going to finish the main story first and then I'll decide if I want to get this expansion (now) or not.