Google Chromecast 3?

I would like to get the Chromecast 3 for an older Samsung TV.
How does this work? As far as I know, you can simply stream everything over the screen to the television via Wi-Fi.

Would like to watch Netflix, Disney + and Youtube. Is it all supported? Is it just an app or do I always have to stream with my phone connected?

The latest Chromecast can do everything on its own, no app required. I don't think the older ones, like without a remote control.