Is this TV bright enough for direct sun?

Sylvox rates the Cinema line for full-sun use, and the Mini-LED backlight pushes high brightness. In shade or at night you will likely turn it down.

Can it stay outside all year?

It is built as an outdoor TV with a sealed, weather-resistant body. Very cold climates and salt air still call for care, and check the rated operating temperature.

Does it need a soundbar?

It supports Dolby Atmos, but built-in outdoor TV speakers are usually modest. A soundbar or outdoor speakers will give much better volume for a patio.

Is 120Hz useful here?

Yes for sports and console gaming, where motion looks smoother. Movie fans will see less benefit unless the source supports it.

How does it compare with indoor TVs?

It trades dark-room picture refinement for brightness and weather resistance. A cheaper indoor TV will look better inside but will not survive outdoors.

What do I need to mount it?

A sturdy wall or ceiling mount rated for the set's weight, plus power and Wi-Fi or Ethernet at the spot. Confirm the VESA pattern before buying a mount.