I would agree that using solid wood is a step up from veneered particle board in terms of longevity and durability. But they still use the same joinery system, those pin-and-latch things plus unglued dowels as alignment pins. These do offer the ability to disassemble the furniture in the future but every time you lean on, bump into, or otherwise apply a racking load to the piece, all that force is going to get transferred to the tiny amount of wood fiber surrounding those screw threads holding those latch pins in place, and eventually they'll start to loosen. They're still not as solid as a good old fashioned glued mortise and tenon, dado or dovetail joint.

Stain can be really difficult, and the real shit of it is cheap woods like pine, poplar and birch that you'd likely want to stain are the worst at it, they tend to come out blotchy. My recommendation is maybe add some tint to the top coat to steer the color in a direction you want but generally pick a wood that is the color you want already.