Do you think ProtonVPN is bad choice for privacy even if your main usage is 4K streaming?
I don't know (never tested it).
Can you suggest another VPN with better ToS/privacy policy which also promise it's suitable for 4K streaming, have very high bandwidth or low delay?
For Mullvad, I've never tried 4k streaming either. But it maxes out my internet connection when I'm downloading stuff.
For streaming, I can imagine the server location matters a lot, and ideally the VPN server should be in between your location and the streaming server.