Can this laptop handle 4K movies and sports very well streamed online?

4k has multiple resolutions depending on aspect ratio and industry.

3840x2160 is the standard 4k called UHD-1, it's the most common usage of 4k in consumer electronics. As a point of reference Youtube, Netflix, Amazon, and network TV stations have standardized on UHD-1.

Another popular version include UW4K for ultra-wide presentation, popular in movies at 3840x1600, but this just means you have black bars on the top and bottom of if you have a 3840x2160 screen.

So either way, your 3840x2160 panel will be 4k friendly.

As for the GPU, I couldn't pull up your config and the relevant GPU so I'll just say that if your panel can do 3840x2160, it would be really poor design if the GPU couldn't handle that resolution at least 24 fps. Good luck!