I recently hit the 3 year mark of being tobacco free.Immediately I didn't even question the possibility that the evaporation/aerosol inhalation of two of the most commonly encountered food, cosmetic, and hygiene chemicals, glycerin and propelyne glycol, would be harmful whatsoever.I heard the hype, I asked doctors. 

It has something to do with nano particles or something like that.)  

He uses an aerosol spray to get every nook and cranny.

The materials used in making these drive the quality and the cost;  - Particle board (and there are different grades of this) is the cheapest  - Plywood is better (again different grades)  - Solid Wood is best (and again different types)Water is the enemy of wood in general and cabinets specifically due to humidity and leaks so I prefer solid wood frame with plywood decks / shelves.

The problem is that 50% of the walls in the house are covered with particle board (like the stuff in the pic, I found that on google; not from the house) and painted over with glossy paint. 

The rep at Home Depot said you don't need any particle board or U lay installed underneath the vinyl plank flooring.

They are generic looking particle boards with fake blond oak look, 1/2" thick.

Particle board or plywood built into the cabinet. 

He seems a little desperate and kinda bugging me with over friendliness which I imagine is because of his physical challenges, I'm guessing but he seems friendly and skilled enough and we'd be working together replacing doors and refinishing/painting that formica covered composite wood stuff the boxes are made of and replacing the (horizontal) particle board.

For your kitchen, if you must replace cabinets, give serious consideration to plywood boxes, vs particle board.