How tall is each stand, and how much room does it take up?

Each stand is listed at 36 inches deep by 12 inches wide by 12 inches high, so it is tall and narrow rather than wide. That shape suits corners and tight walls.

How many plants fit on one stand?

There are three tiers, so each stand holds up to three pots, with the drawer below. Tall or wide pots may not clear the tier above.

Does it come with anti-tip hardware?

Yes. The set includes anti-tipping devices for securing the stands to a wall, which matters on a tall, lightweight frame.

Can it be used outdoors?

It is sold as an indoor plant stand. The metal and drawer are intended for indoor use, so a covered porch is a safer bet than full weather.

Two three-tier metal plant stands, each with a drawer, plus the anti-tipping devices. Assembly is required.

Is it worth it against a plain shelf or a wooden stand?

It gives you two tiered stands with drawers for the effort of one purchase, which beats a bare shelf for plant display. A wooden stand will look more like furniture but usually holds fewer pots.