Will this lip scrape or hang low on speed bumps and driveways?

The front lip mounts to your existing bumper, so ground clearance stays the same as stock. Approach angle is unchanged. If you already navigate speed bumps and parking lot inclines without issue, the lip won't change that.

Is FRP rigid enough, or will it flex and crack?

FRP is a hard panel construction designed for street use. It won't flex like plastic trim or urethane bumper covers. Normal handling and parking lot speeds present no risk; it's built to stay put and last.

Do I need hardware to install this, or does it come with everything?

The lip assembly is included. For fastener details and torque specs, reference your vehicle's service manual or OEM bumper documentation. Most installations use existing bumper holes, so you may already have what you need on hand.