Honestly as a hobbyist who has spent hundreds of hours working on custom pieces and hundreds of hours working on my own home I recommend an affordable plywood in a pine or poplar skin, and then use poplar as a finish/ trim. Poplar is still a lighter material very affordable from most mills that arent mega stores like lowes or hd. It sands well, has zero sap, minimal knots, and paints or stains really well. The plywood even a cheaper variety will hold almost any amount of weight you put on it as long as you tie the structure into your studs.