Does a streamer do anything to the data that Tidal provides?

Why would you want a streamer or a computer to act like a streamer these days? I got rid of my dedicated Mac mini running various audio software (pure music, audirvana) years ago. This setup bettered than a multi thousand $$ CD player which I sold. It is foolish imo to have a computer in your audio room.
i moved to a dedicated streamer the Auralic Aries which bettered the Mac mini setup by quite a bit. The drawback was using usb to an external dac.
for a year now, I have been using a bridge that’s built in to a ps audio directstream dac. Internally it uses an i2s interface between the bridge and dac. I use roon and SQ is fantastic. Last month, an audio publication had a review of a DCS bridge which they really liked.
if you don’t want the best setup using a bridge, the Aries with its DS Lightning software was very good.

+1 on Aires though i run the Mini via spdif to an Audio Note DAC-3 signature. Love the sound and the Lightning DS app is great.

+1 on Aries.
I purchased Auralic Aries Femto to streamline and simplify my music listening - but some of my gear already had streaming capabilities. I was never satisfied with minim server on my NAS and used JRiver. To my surprise Aries also greatly improved sound quality. The most glaring difference in quality was AES/EBU out from Auralic compared to OPPO 105 SPDIF out (I for years use Jriver and BubbleUPNP to play my collection via OPPO).
In fact, to my amusement OPPO-105 as a DAC (I am not using it now in that capacity, but it is still a pretty good one) sounded better when fed from Aries then if used build-in streamer. Dunno why.
To sum up I do not believe that "all streamers" are the same and "digital is digital". Will the  difference in sound justify the price - it is a different story.

On a similar note, what is the best option for internet radio these days?  I don't want to stream from my computer, and listed to my local radio stations a good deal (most of them have internet radio presence).  I might want to stream some music from Amazon Music from my iPhone.  What would be the best solution here?

@willemj I do not see a digital output listed on the Chromecast Audio specs.

Let me reassure you. I have a few Chromecast Audio streamers, some using the analogue output from the internal DAC, others using the optical digital output. The digital output uses the mini optical connector into the same little slot as the little analogue output does, in the same way some Apple products do. For a test, see here: http://archimago.blogspot.nl/2016/02/measurements-google-chromecast-audio_27.html
The digital output is a relatively unknown feature. I have heard from several people who, like me, were told in a store that the Chromecast Audio only has an analogue output.
On the software side, I am happy with the TuneIn app. It even has a sleeptimer.