Does it keep filament dry?

No. It is an open metal rack, so spools are exposed to room air and humidity. Pair it with sealed dry boxes or desiccant if you print hygroscopic materials like nylon or PETG.

How much weight does each shelf hold?

The maker does not publish a per-shelf weight rating. Full 1 kg spools are well within what a metal cart of this type handles, but avoid stacking multiple spools per shelf.

Can I lock the wheels?

The listing does not state whether the casters lock. Adjustable feet are included, so you can level the rack and keep it from rolling if the wheels are not braked.

Does it fit large spool sizes?

No spool diameter or shelf clearance is given. Standard 1 kg spools should fit; check the shelf gap before buying for 2 kg or oversized spools.

The rack, its wheels and the adjustable feet, plus assembly hardware. Spools and printers are not included.

Is it worth it over a plain shelf?

If you want filament to move with the printer and don't need moisture control, the wheels and metal build make it more useful than a static shelf. If dryness matters most, spend on a sealed dry box instead.