8GB is enough for 4K streaming.

No. 4K video playback in Chrome or Edge is not going to push past 8GB of RAM unless you also have fifty tabs open that are all running heavy sites.

Streaming 4K video is mostly a GPU and codec thing (or your internet connection). RAM usage for a single 4K tab sits somewhere around 500MB–1GB. Your OS and background apps might add another 3–4GB. You have to try pretty hard to hit 8GB.

If your playback is stuttering, it’s probably because your CPU is old, your GPU can’t decode HEVC, or your Wi-Fi is weak. Not because you ran out of memory. Check those first.

16GB is nice for multitasking, but don’t buy it just to watch Netflix in Ultra HD. You won’t notice a difference.