Difference between app on computer vs smart tv or streaming devices

Hope this is posted in the right place.

What differences are there between the music streaming services when accessed via:

pc
smart tv
dedicated music server/streaming hardware

Will I notice a difference between utilizing web version via a laptop connected to my AV preamp vs... just using app via roku or smart tv app?

And how much better is a dedicated music server etc?

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And - how do I make the most out of using each of these?  What cables do I need etc? USB vs cat vs hdmi etc... 

DAC vs no dac?  And what is the cheapest dac I could get - that would significantly improve the sound quality?

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