Mine uses 4×4 fence posts for the legs,with 4×2 stretchers morticed and tenoned into them, with the tenons then pinned with dowels. Top is 25mm MDF but kitchen worktop is ideal. I wouldn’t use a door as they tend to be thin ply over a light wood frame, which I’d not trust with heavy bench tools, or doing any serious work on. As for’ over engineering’; one of the most important aspects of a proper workbench, is solidity. You don’t want it wobbling about as that could even be dangerous. Strength is important if you are going to use a proper vice; you don’t want it shearing away and falling on your foot!
“This sort if overlapping structure is much easier to build than the one in your link”
It’ll be ok for occasional work, but any serious use will soon shake something like that apart. I’ve seen quite a few benches like that break. There’s a good reason proper woodworking benches are made in a particular way. My next bench will be made out of oak and/or beech.
I’d also avoid wheels unless you really need it to be movable, as they just make the whole thing wobbly, even with the castors locked. The type of wheels which are ‘retractable’ are the ones to use, so that the structure is sitting securely on the floor.