If you use Spotify it's relatively easy to setup the Pi as a Spotify Connect player. This allows you to select it as a playback device from the Spotify App when both devices are on the same network. That way the music is streamed directly from Spotify to the Pi and it doesn't drain your phone battery like Bluetooth does. Also, no issue with range since it will keep playing your selected playlist even when your phone leaves the network.Is it possible to connect the phone/tablet/pc to the RPi trough network instead of BT?
This is true, the default audio out of the Pi is fairly low quality. I use a HifiBerry Dac on a Pi Zero W and it works great. Although the Zero of course doesn't have an audio out, so a hat is compulsory anyway.Buying an inexpensive DAC board for the pi is the way to go if you want to compare it to the sonos for example. There are PCM5122 based sound boards for about 20$ and this increases the pi sound quality VERY much.
Yeah, not sure what you're talking about here. The pi4 does have a higher clock than the pi3, but they are both in the GHz. It's not clear how that change in frequency could induce audio interference?Even with a DAC board the raspberry pi4 is a bad choice for audio reproduction. Its high frequency CPU induces so much electro magnetical interference, that you either need to underclock it a bit or at best take the raspberry pi3b. Its EMI numbers are much better and do not disturb the amplifiers speakers so much. Faster is not always better. The Pi3b has all the features needed here too, like Wifi and BT.