PCM 2 means that the box outputs stereo, doing a conversion from 5.1 if necessary.
PCM 5.1* means that the box outputs 5.1 if it receives it and the TV converts to stereo.
Either way there should no audible difference from a TV's speakers.
* Use this if you have a sound system of 3.1 or better.
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Hub 3.0, TP-Link Archer C8, TP-Link TL-SG108S 8-port gigabit switch, V6