The QuickStart mode is just this, a fast layout, that you can use or just bypass it.
Therefore, after you press the "Continue" button you will be able to save, import, trace, print, move, use the Power Tools, set the precision and units, as well as use all the Punch features.
In project mode, you can define manually the length of the walls, for example.
Punch, as any program, has a learning curve. The best way to learn the program, IMO, is practice + practice + practice => Read and follow the manual (this is important), see the videos => try to create elements not related with your project, so you will become familiar with the commands and how to manage the different components and solutions .
Keep in mind that Punch is a Home Design program, so, differently of Corel Draw, or Paint or CAD (they are drawing programs) you must follow the different steps to create the different building components.
Hope this helps.