Fairly new to streaming. Where to start?

If you're looking for a way to try out streaming, consider the Sonos Connect (which you could probably pick up for cheap on eBay these days.)  I'm using it as a Roon endpoint and feeding the digital output directly to the (way higher quality) DAC in my HK990 integrated.  Streaming TIDAL and my own HDTracks content from my NAS, the results are really good.

1) I have a Roon server with a couple of thousand CD tracks ripped to ALAC, vinyl tracks also ripped to ALAC, several albums worth of FLAC content from HDTracks, and a TIDAL subscription. For me, if I’ve got local digital copy, I listen to that (less impact on my internet feed). If I have a worn (albeit cleaned up) track on vinyl and it’s available on TIDAL, I listen to the TIDAL copy. So, the advantage I find is I can always find the cleanest copy somewhere. Disadvantage? If you’ve got limited internet bandwidth, you’ll get choppy/crappy  quality from your stream.2) Um, no.3) AFAIK TIDAL and Qobuz highest quality streams are pretty much equivalent; I don’t have SACD, but I would say that in comparing my HDTracks content to the equivalent content on TIDAL, HDTracks wins. And certainly playing CDs on my H/K HD990/HK990 combo is better than TIDAL. But it’s the AMOUNT of high quality content on TIDAL that is the compelling factor in getting a subscription.4) You need a box with computing power that will receive a streaming signal, and an RCA stereo cable to connect it to an AUX input on your amp/receiver. I use a Sonos Connect and feed the digital output to the DAC in my HK990, and it’s great.