I'm interested to know people's approach to this type of situation, this example will be more familiar to people in the UK but I'm sure there will be other similar situations.
If you use corridors it's easy to create a Template which has a kerb, concrete surround and the footway construction interfacing with the two correctly, as you would show in construction details, example below:
The question is if you are using Surface Templates e.g. run the kerb/concrete surround Corridor along the channel of a traffic island and fill it in with footway construction using a surface template. The footway construction would overlap with the kerb concrete surround.
One option is to accept overlap but I would expect the overlap everywhere, not just where Surface Templates are used. Another I can think of is to include a bit of footway behind the kerb in the Template/Corridor which can target a surface to follow the Terrain behind it but doesn't seem like a robust solution.
How do people go about doing their models?
Yes, create both front and back using whatever method fits the problem, but make sure you can grab geometry from it to create a surface.