Will the carbon fiber pattern fade or yellow in direct sunlight?

The injection-molded finish is UV-stabilized to resist yellowing. It won't need a clear coat to maintain color, though keeping the surface clean extends the look.

How do these mount to the window frame?

These are designed for factory window channels. Test-fit before committing to adhesive or fasteners—mounting hardware not specified, so verify your preferred attachment method fits your install.

Do I need to seal the edges where the visor meets the glass?

The edges are finished as-molded. If you want to seal gaps against water intrusion, apply weatherstripping or trim-seal to the mounting surface before installation.