Can I lock the cabinets together when they're stacked?

Locking mechanism details aren't specified in the product data. Test the connection before loading heavy tools — you may need to secure them with fasteners or a chain if lateral movement is a concern.

Do the casters lock to keep the cabinet from rolling?

Caster type and locking feature are not confirmed. Verify whether brakes are included before assuming the cabinets will stay in place on a slope.

What's the weight capacity per cabinet?

Weight limits aren't specified in the available data. Contact support with your tool inventory weight before committing — it'll determine how you should distribute load across the two units.