If you want the highest quality of picture and sound, you're going to want HDMI cables. For your Ultra HD Blu-ray player or 4K streaming device, make sure to get a 4K-supported cable, like this 6-foot high-speed 2.0 HDMI cable for $12. Then check your TV manual to see which ports on your TV you should be using for UHD.
See: https://versuscomparison.com/qn85a-vs-qn90a/
If you want the highest quality of picture and sound, you're going to want HDMI cables. For your Ultra HD Blu-ray player or 4K streaming device, make sure to get a 4K-supported cable, like this 6-foot high-speed 2.0 HDMI cable for $12. Then check your TV manual to see which ports on your TV you should be using for UHD.
See: https://versuscomparison.com/qn85a-vs-qn90a/