Hello there, B Reiff. Thanks for sharing your concern in the Community forum.
The number of items you set up and what item consists of that assembly depends on you. Also, QuickBooks Desktop has an option to automatically create sub-assemblies. If you consider using this feature, you can follow the steps below:
1. Go to the Inventory menu and select Build Assemblies.
2. Tick the Automatically build required subassemblies option.
For more tips and information, you can use this article as your guide: Create, build, and work with inventory assembly items.
Comment below if you have other questions. Take care always and stay safe.