Bluetooth or not

Chromecast audio is another solid approach but I think it only works with apps that are cast compatible. PLEX would be one option for in-home streaming. I’ve seen that work with Chromecast and Google home devices in my house but have not tried Chromecast audio yet.

It will depend case by case. DAC used is the biggest factor. Newer Bluetooth technology can be quite good.   Traditionally, wired has greater upside.   Try both and see.

Using a good outboard dac with wired connection is probably the surest bet for best sound. I’ve gone that way with a Chord Mojo DAC. Not only is it great with headphones but as an input to a good hifi as well. I went for bust and connect it to line level inputs using a very high quality Mogami gold mini stereo to dual RCA Y adapter. The results are absolute top notch.