Correct, you would no longer be using the streaming function of the LG OLED. The LG TV would now become only a video output display device.
Yes, both audio and video signal would be part of the HDMI cable connection from the Roku into the Lyngdorf. The Lyngdorf would pass along the HDMI signal to the TV so that you get video.
You are correct in all your assumptions.
Using ARC is sort of a backward way to get a digital audio signal "generated" by the TV (using either a channel tuning or a streaming app in the TV). It is not as good because you are limited to old school Dolby Digital / DTS and it uses a single wire in the HDMI cable to "talk back" to the Lyngdorf. You will have to manualy switch the Lyngdorf into "ARC" mode when you want to do this. However, it's always better to use a real A/V source to supply audio/video into the Lyngdorf, such as a Roku or a bluray player.
ARC was developed really for those types of people who just want to throw a TV up on the wall and expect it to do "everything", but then later wanted to add an audio system into the mix as easy as possible. They don't want to mess with different sources (i.e. Roku, bluray, satellite receiver, etc.). ARC is not the "audiophile" way to go. It is really a "convenience" feature.
Yes, both audio and video signal would be part of the HDMI cable connection from the Roku into the Lyngdorf. The Lyngdorf would pass along the HDMI signal to the TV so that you get video.
You are correct in all your assumptions.
Using ARC is sort of a backward way to get a digital audio signal "generated" by the TV (using either a channel tuning or a streaming app in the TV). It is not as good because you are limited to old school Dolby Digital / DTS and it uses a single wire in the HDMI cable to "talk back" to the Lyngdorf. You will have to manualy switch the Lyngdorf into "ARC" mode when you want to do this. However, it's always better to use a real A/V source to supply audio/video into the Lyngdorf, such as a Roku or a bluray player.
ARC was developed really for those types of people who just want to throw a TV up on the wall and expect it to do "everything", but then later wanted to add an audio system into the mix as easy as possible. They don't want to mess with different sources (i.e. Roku, bluray, satellite receiver, etc.). ARC is not the "audiophile" way to go. It is really a "convenience" feature.