Should all parts of a physical object be modelled as a single Blender object? I have some experience with 3D parametric CAD (e.g. Solidworks, Autodek Inventor). So far, I have watched the official Blender tutorials 3 times and read a complete book about Blender. I am wondering if I will need to undergo a paradigm shift to successfully model in Blender.
Suppose I am drawing a wooden stool. In parametric CAD, I would design a leg (1 object) with a hole that fits a screw, make the seat (another object) with 4 holes for the 4 leg screws, and make a screw (yet another object). Then in the final assembly, I will assemble 4 legs and the seat by putting in 4 screws. Drawing finished.
What is the process in Blender? Do Blender users make only one object called &quot;Stool&quot; and model the shape of the stool without regard for the components of the object (e.g. legs, screws, seat)? What if the screws are important (e.g. I need to be able to accurately take the stool apart)?
There's a question you need to answer before asking: 'How do I draw this stool?'.
It's: 'Why am I drawing this stool?'.
If you're using a CAD package, the answer to the latter is usually given. It's to propose, or to aid, the manufacture of a real-world stool. But if you're using a visualizaton and animation suite like Blender, that's not the case.
It could be:

A stool to illustrate the assembly of stools, including the deployment of screws
A 3D-printable stool, with a manifold surface.
A pre-lit low-poly stool, for use in a limited-resources game
A hero foreground stool, with wood grain and shiny screw heads, in an
architectural visualization, or product shot.
A graphic stool, for use in a poster advertising a chain of cafés
A hacked out-of-focus background stool, only half of which is ever seen
A toon stool, which can run away from its obese owner, and attempt suicide by jumping out of an apartment window
A stool for sale as an asset to be used by other people, whose purpose is part of its advertised specification, and needs to be by-the-book
A photorealistic VFX stool, which will need to bounce off a previously filmed floor, and be shot to pieces in scene 23
.......

These are considerations unlikely to be taken into account by a CAD user. There's no single paradigm. Each stool will require a different approach to serving its purpose, while avoiding as much work as possible.