Whether a native mobile application such as an iOS or Android app is appropriate will depend on your business aims and objectives. In most cases a website is the appropriate choice.
The acronym CMS stands for Content Management System. These allow the structure and visual design of a website to be developed by a web developer initially then content may be added and maintained by the client.
Web design professionals use a grid layout to provide a consistent look and feel for websites. Grids have a long history of use in print design.
Responsive design is mostly suitable for situations where it is desirable to develop a single website that is accessible across multiple types of devices, i.e. desktop, labtop, and mobile. Whether it should be used needs to be considered on a case-by-case basis.