I always go back and clean up the geometry in the end, but for WIP renders, I don't care as long as it looks right.

Create inorganic surfaces with compound curves and put openings with sharp irregular corners with fitting covers. Round is easy, sharp corners are not.

And as far as booleans are concerned, I think they fine to be used whenever they can speed up your productivity, and you clean up the resulting geometry. This is what I have always maintained. I don't believe the quantifier "use sparingly" applies. Use whenever it makes sense and improves your workflow. "Use sparingly" implies "Use only as a method of last resort" to many people. You will never learn to use a tool if you avoid it like the plague many want to make them out to be!

Go back though all my work, you will find exactly one thing I have modeled with an n-gon. My final products are always quad with a couple scattered tri's.

The only final thing I posted with 5-sides and n-gons was the bottle cap based on a design used by a professional modeler working in the art department at coca-cola.

Even my mech, based on a 3d-palace max tutorial, is all quads and the tutorial version has many 8+ sided polygons and surfaces with 50-sided holes even! In fact I have several max tutorials and ngons in planer faces are used all willy nilly in many of them.

The 3D-Palace max tutorials and WIPs REGULARLY create models that have 8+ sided n-gons all over the place and rarely ever build anything to be smoothed and build models with the highest poly counts I have ever seen.