Can these boxes be stacked or wall-mounted?

These are designed as standalone storage units. Stacking is possible if weight distribution works for your setup, but mounting hardware and method aren't specified — test your configuration before committing to wall installation.

What's the best way to organize tools between the two boxes?

Separate by tool category — hand tools in one, fasteners and small parts in the other. Or split by project type so you grab the right box when you need it. Hard panel construction keeps everything protected either way.

Do these come with latches or locks?

Closure type and security features aren't confirmed in the product specs. Verify before purchase if locking or weather sealing is critical for your storage situation.