FINAL UPDATE
Support confirmed that nothing is wrong with my FW16.
I therefore ordered a Baseus 140W charger, and when it arrived… Oh boy.
The performance was super consistent. GPU power draw around ~70W in balanced, 80W in high performance. This charger just… Works. No weird negotiation issues, nor swinging power draw. It just works as you’d expect it to. Not the full power you get with the 180W stock charger, but close enough.
I’ll probably cross-post this in the FW16 main thread, so people don’t waste 110$ on a charger that can’t do it’s job well enough.
TL;DR: DO NOT BUY UGREEN NEXODE X 160W. IT WILL NOT WORK WELL with the dGPU