As a previous user, I wouldn't recommend you getting that system. Firstly, if your tank is only a 30 or 40cm cube, the width is already going to take up 10cm of your tank space.
In order for you to maximise your space, I would say get a cheap china cannister filter e.g. weipro or Jebo/jebao, run carbon and phosphate media in it and then get a skimmer. For lighting, you might want to consider those clip on LED lighting and for corals, get those that do not require bright and strong lights. Fishes, get 2 or 3 small fishes would be enough.
HOB filters may be able to be used but you must get those with larger media compartments. Skimmer wise, get a HOB one or if you are able to change 20% of water weekly, then u may not require a skimmer.