Creating arched walls and ceilings can be tricky, especially in Chief Architect. Have you tried using the polyline solid tool for the curved walls? For the ceiling, consider using manual soffits to achieve the desired arched effect.
It sounds like you're experiencing an issue with picture settings on your camera. Have you tried adjusting the resolution or aspect ratio before saving the image? This can sometimes help avoid the squished appearance. You might also want to check if there's a specific setting for image compression that could be causing this.