The management portion of the game is not essential to play, however it will make the end game far easier. The only element that are sort of required is Nova's politics tab, however at present this is just making 3 selections.
With the game I have tried to automate where possible, however if I automate everything, then I may as well skip entirely. Whilst some would would prefer just a VN, I have elected to create something a bit more involved.
For those that haven't jumped into the mechanics, after selecting a contract to say make 3 Sandgropers you can have these made by the following. Go to assembly, find Sandgropers and increment to 3. Go to manufacturing and click the robot head to queue up all required elements and then click on ingots button to procure all required metal. When manufacturing is complete, then it's just a matter of going back to the contracts page to finalise. Relatively painless considering the complexity of the manufacturing process.
As far as harem questions:
There will be an opportunity to play the field, however as in real life if you want to explore a relationship more deeply, then you will need to be more faithful to that partner. Of course how faithful you need to be will depend upon the partner.