If you do want to use equipment from Europe in a residence one thing to keep in mind is their standards use a 'RCD' residual current device in the breakers or what I call a class B GFCI manufacturers now call it Ground fault protection of equipment (GFPE), with a 30ma ground fault trip instead of our 5ma.
I learned about this years ago when working with commercial espresso equipment, the manufacturer in Italy got their equipment NSF/ ETL certified in the US and Canada but you still had to use those GFPE breakers per the listing.
Now that the NEC requires GFCI in commercial kitchens they are just on a GFCI breaker.
So in a residential setting where a GFCI is required you'd need a 2 pole GFCI and where one is not required I'd recommend using a 2 pole GFPE breaker, Siemens and Eaton do still offer them for their plug on load-centers.
I would not recommend using NEMA receptacles, as there is more possibility of the end users messing up the cords cutting and re capping all their appliances. I'd try find some suitable Shukos' that mount on a regular 2 gang box, never looked but you might even find some ETL listed ones.
Also I would not worry about Line to Neutral or Line to Line, Line to Line here in the US would just limit the maximum potential to earth to 120V. Its just more expensive as you need 2 pole breakers and switching.
Cheers
