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Domino and rafix, no clamps required, everything can be assembled on site without glue. Also works well for freestanding furniture.
https://www.hafele.co.uk/en/product/connector-housing-plastic-rafix-20/P-00861352/
Screwing boards into the edge of boards is pretty basic. There are advantages in screws developed to do it but modern MDF is so fluffy in the centre there's barely anything for a screw to hold onto.
Domino is easily worth it for a professional, biscuit joints are a more accessible method if you can't justify the domino. Biscuit joints + screws can work ok.
12mm MDF doors are a bit flimsy, Tricky getting hinges on/in them too. MRMDF not really a requirement (he says standard on pro builds but that's not been my experience) and ply for the shelves is overkill. The drawer runners are not that nice. All screwed together too, hello 1990's šš».
Fairplay for the hand design work, it's been a long time but I have a few notebooks like that.
Don't do overlay doors, but a really nice finish is doubling up the mdf and inlaying the door with an overlay set back behind it. Keeps them airtight if you get it right.
What a game with the plinth, it's a lot easier with a laser. Can't make my mind up about the way he finishes the plinth but I've never thought to do it that way.
There's a great tool for handling MDF sheets https://www.amazon.co.uk/Gorilla-Gripper-Multi-function-Farewell-Backache/dp/B07TV51JV4