Is this card fast enough for 4K video?

Yes for casual 4K clips. The V30 rating guarantees a minimum sustained write speed for video, but the card's write speed is modest, so very high-bitrate recording may not keep up.

Will it work in a Nintendo Switch?

Yes. The Switch accepts microSD cards up to 2TB, and 512GB is enough for a large game library. Owners report it works with no setup beyond inserting it.

How is it different from SanDisk Extreme cards?

The Ultra line is the value tier. Extreme and Extreme Pro cards have faster write speeds and higher endurance ratings, which suit burst photography and sustained video better.

Do I need to format it before use?

Usually not for phones, tablets or the Switch, which format the card themselves. Format it in the device you plan to use it with, especially for cameras and dash cams.

Is it good for a dash cam or security camera?

It works, but it is not a high-endurance card. Continuous recording writes heavily and wears cards faster, so a card rated for surveillance use is the safer long-term choice.