If you go to a company for an interview or discussion, the other party will not give you much time to make it with software, so hand-drawing is really important. Just remember that stupid birds fly first ~
The most basic learning software for interior design major is 3DMAX and CAD, and Photoshop is the most basic ~
Lightscap is also known as "rendering master", and Vray is also a rendering software. You can choose one of these two.