Are the wheels lockable?

Wheel locking mechanism not specified. Test the cart's mobility before committing to a permanent spot in your workspace — you may want to add aftermarket locking casters if stationary positioning is important.

What's the weight capacity per tray?

Capacity specs not provided in the product data. Load it conservatively with hand tools and small parts, and avoid stacking heavy engine components on a single tier.

Can I bolt this to the floor or is it mobile-only?

Designed as a mobile cart with wheeled base. If you need a stationary workbench, anchor points aren't confirmed — keep it rolling or source floor fasteners separately.