There's one (and a half) last scheduled sleeper train in Japan (as distinct from luxury cruise trains), the Sunrise Izumo / Sunrise Seto, which has fairly reasonable prices, although as you say it's a conventional train and much slower than the Shinkansen.

The trains you link to only go at 150km/h to minimise noise, so using ⩾300km/h-capable rolling stock might be a bit of a waste.