LG OLED

I'm awaiting delivery of an LG 55EG9100, but this question probably applies to most of the LG OLEDs. There are two audio outs on this, S/PDIF over toslink and HDMI/ARC. For the output, you can choose either "auto" or PCM. For "auto," the format will depend on the source and can be PCM, Dolby digital, or DTS/PCM. The way the menu is formatted, it suggests all of these are available on both ARC and TOSlink.

My question is whether anyone knows whether the TV mixes down the various channels to 2-channel PCM or whether it is sending multi-channel PCM? If it is 2-channel, which I suspect must be the answer for Toslink, does anyone know whether it is being intelligent in the mixing vs., say, just taking a pair of L/R and dropping everything else?

I want to put a cheap DAC on the toslink to add headphones or feed into an old analog Adcom pre-amp. The answer to the question determines whether that DAC needs to be a 5.1 channel to L/R or it can be a 2-channel DAC. For a 5.1 DAC, I'd probably use the Orei DA34 and for a 2-channel I'd probably use the Schiit Modi 2 Uber. I should say that I'm not trying to get great A/V sound. I just want basic function so that I can focus my resources on upgrading the existing 2-channel audio system for music in the future. (Please don't let that last comment distract us into A/V vs. hi-fi/audio :-) )