Will this lip interfere with my OEM bumper or headlight assemblies?

The ZLR lip is designed for the factory front-end opening. Before installation, verify clearance at the outer corners where the lip meets the bumper trim and confirm your headlight housings sit flush. Minor fitment gaps are normal and can be addressed with shims or strategic adhesive application during final assembly.

Should I drill through the substructure or use adhesive to mount this?

FRP lips can be secured either way — adhesive-only setups reduce drill risk but demand immaculate surface prep and cure time; drilling offers mechanical security if you're confident in your hole placement and fastener choice. Sand the mounting surface thoroughly, degrease it, and match your method to your vehicle's existing lip mounting strategy if one exists.

Will this stay stable at highway speeds, or does it need additional bracing?

FRP is rigid enough for street use without supplemental support if mounted securely. Wind buffeting and road debris are the main stressors — ensure all fastening points are torqued evenly and check them after your first 500 miles. Adhesive-mounted pieces benefit from a full cure period (24+ hours) before sustained highway driving.