Will the carbon fiber yellow or fade in the sun?

Carbon fiber resists UV damage far better than OEM plastic or paint. The glossy finish is factory-sealed and will hold its color for years with normal exposure. If you park under trees or live in harsh sun, occasional rinsing keeps it looking new.

Do I need to seal the edges where the visor meets the window frame?

The mounting points use factory holes that are already sealed. Edges where carbon meets glass don't require additional sealant—water drains away naturally. If you want extra insurance against water creep, silicone caulk works but isn't necessary for normal use.

Is this wet or dry carbon, and does it matter for durability?

These are finished carbon fiber with a protective glossy topcoat. That sealing layer is what protects against UV and moisture—it's the same approach used on high-end carbon hoods and wings. The finish is what keeps the weave looking sharp and prevents degradation.