We want to change the output look and feel according to our brand.
How we can do effectively?
We are using RH-2017
The layouts allow various customisation and the appearance of topics is down to what you set up in the CSS. Those are your options and you have to design accordingly. It's up to your design skills within those parameters. It's a very broad question.
See www.grainge.org for free RoboHelp and Authoring information.