The dual-meter system with a mechanical timeclock sounds very much like the old white-meter system that was used here. I don't think any PoCo still offers it as an option, but there might be a few still in use somewhere.
The storage heaters here also use individual radial circuits, one per heater, rated 15/16 or 20A.
Water heating arrangments vary somewhat. In setups such as the one pictured above and where there is only a single element, it's quite common to install an individual timer for the immersion heater which can be adjusted by the homeowner as required, and also allows for manual boost during the day.
Dual-element systems used to be quite popular, sometimes with the main (lower) element wired to the night meter circuits and the smaller (upper) element on a manual switch with power available all day.
A common sight at one time was a twin switch, one marked ON/OFF and the other SINK/BATH, which transferred power between the upper and lower elements.
