Neutral Scene_Function and Application

As an individual noob who has been exploring UE4 alone, I always meet a lot of issues when taking my little experience. Sometimes I find some good tips and tutorials giving me very good information. However, many of them are very fragmentary, such as how to create photorealistic production rendering by using studio lighting. They are good, but not suitable for a beginner like me because I need to understand the whole workflow.

Recently I watched the lighting master class. Although that tutorial seems to focus on beginners, I still found something confusing to me, so I post this to find someone who could kindly answer my stupid questions. In the tutorial, the lecturer mentioned in order to get good lighting, it’s better to create a grey sphere and a chrome sphere as references for mid-grey and reflection. However, can anyone tell me the right and detailed workflow of using these references to improve the lighting? For example, how can these spheres help if I want to create photorealistic lighting for archviz project?