I have no experience with this Indian Smartbin system myself, but it looks like it is a Bokashi system. I suspect that the only difference with other commercial systems is that they sell their own mix of Effective Microorganisms (EM). This mix is probably slightly different from the already existing and trademarked mixes, but the principle of how to use it is still the same.
From what I've gathered on the website the Smartbins are airtight (this is necessary when composting with EM). This means that if the bin is closed, there is no chance of any odors coming out. However there probably is a soury smell if the bin is opened, for example when you add more food scraps or when you add the compost at the end of stage one. Usually the smell is nothing too bad, but if you dislike it you may want to open it outside.
I see no reason why the Smartbin cannot be used by a family of two, or by a single person for that matter. You just gather all your food scraps until the bin is full (or half full is you leave space for adding compost later). If you don't generate much food waste just make sure you use a small bin.
If you want to DIY, you'll have to buy your own airtight bins. There are many tutorials on the internet, for example this one is very easy to DIY or you can create one with a tap to drain fluids more easily.
Besides a bin, you need to create an EM starter culture. Again there are many tutorials on the internet, here is an example. Note that creating a EM culture will take about 3 weeks and you'll have to create new EM every now and then when you run out of it.