• No SBC that I know of can handle 4k 120Hz HDR output, so getting the most of moonlight is not possible.
• Low latency decode requires some work to get running
• AV1 encode/decode has even more latency, do you will be running higher bitrate h264, which in turn means wired network connection is recommended.
• Streaming services limit 4k and/or HDR access on a lot of content to locked devices. E.g. Netflix only guarantees 720p sdr when watching in a browser - how much more you get depends on the deal with the copyright holder.

Tl;dr; a long, active fiber HDMI cable + USB over IP might be cheaper, better and easier. That’s what I ended up buying despite the cable length being 60m (200ft).

Honestly, you might be looking at a ShieldTV.

Any Linux distro with Flex Launcher and an Air Mouse+Keyboard Remote.

This is what my HTPC looks like currently:

If you want to be able to use “actual streaming services like Netflix”, you’re gonna be disappointed. Those use DRM that won’t be available to your Pi. Most of them will at least limit the quality to a pretty pathetic level. Overall it’s not going to be a satisfying experience. AFAIK it takes some major hackery to get around that limitation, making it a practically insurmountable obstacle.

Otherwise the rest are more than doable. I’d still recommend an x64 based mini pc though.

There are many multimedia solutions for ARM (e.g. libreelec, kodi, plex, jellyfin etc etc), however, these work best for non-big-streaming sites. The moment you’re after a really good youtube experience, or netflix/disney+/etc, then things start break down for various reasons.

Personally, I’d just install the default Raspbian OS (maybe even just DietPi), making sure that their Firefox or Chromium supports drm websites, and then I’d connect the Pi to the TV, and then I’d use a keyboard + touchpad, like this one: https://www.amazon.com/Logitech-Wireless-Keyboard-Touchpad-PC-connected/dp/B014EUQOGK/ This allows you to use the machine exactly the way you need it to, without bad surprises and incompatibilities. Not the way you want it to, but more like the way you need it to.

Also, please note that if you’re having a Pi with only 1 GB of RAM, it won’t be enough for what you’re having in mind. I have a 3B+ with 1 GB of RAM, and my Emby server (music only!) constantly needs more than 1 GB of RAM, resulting in the Pi to swap, which means that it wears out the microSD a lot.

Finally, if all else fails get an AppleTV, or a Chromecast with AndroidTV, or a Roku if you’re in the US, but I think the desktop/browser solution can be workable. Not pretty, but most workable for DRM streaming services.

https://dietpi.com can be configured for Kodi. Youll be limited to 1080p H264 for streaming, as long as your Plex server can transcode to that format you should be OK.

It’ll probs support any xinput-compatible pad, too.

Not sure about moonlight support on Pi/Linux but again you’ll be limited by the decode.

• Assuming you have a Pi4B, by the way.

I’m about to start my adventure with Raspberry Pi powered TV box. I will try Plasma big screen - https://plasma-bigscreen.org/ It seems like a good place to start.