The showcased models did not feature full integration with Alexa, as the vocal commands only prompt on screen answers instead of voiced answers, but the final products should fix this. Spec-wise, the Yoga 730 impresses with high-end features that can easily rival a gaming laptop, while the Flex 14 is more of a mid-range solution.
https://www.notebookcheck.net/Lenovo-showcases-Yoga-730-2-in-1-with-Cortana-Alexa-assistants-and-Flex-14-notebook.286490.0.html
I'm guessing by the thinner case dimensions on the 730 13"/15" that the 8th gen i7 GPUs are the 8850u. This would be a welcome change from the 6700hq as performance is similar without the power draw. I hope they don't cut down the battery in the 15 but likely will.
I wish the 15" had dual thunderbolt 3 ports like the 13" does. I know they went with the Lenovo power port because of the gtx 1050 gpu option which is beyond the power deliverable over usb-c. But its annoying that the 13" has a better port selection in that regard.
It would be nice for example to have a 15" yoga 730 speced like the 13" with dual thunderbolt ports. Then you could hook one to an dock for ports/power/external monitors and the other to a egpu box when your at the desk. The 15" has a bigger (which to me as better) screen but its less useful othewise.