A:Answer Optical / TOSlink is a very old and it used to be a good method for sending digital sound. That isn't the case anymore. Toshiba invented it in 1983.
TOSlink does not have the bandwidth to carry uncompressed versions of Dolby TrueHD, DTS-HD Master Audio, or more than two channels of uncompressed PCM. And it and isn't compatible with Dolby Atmos.
Get a good 8k HDMI 2.1 cable and connect your TV to your A/V receiver through the eARC HDMI port on your TV. Your sound will improve quite a bit.
As far as picture quality and sound, in general, what you get with more expensive 4k players is this:
Better DACs, better processors for upscaling DVD and Blu-ray to 4k. You get more discreet audio channels if you want to connect component sound directly to the player and you get codec for DolbyVision color (which is better than HDR 10 and HDR 10+). DolbyVision is only going to matter to people with a TV capable of displaying DolbyVision (Samsung TV's ARE NOT COMPATIBLE WITH DOLBYVISION).
I hope that helps you.
