Why in some instances does changing streamers makes a bigger difference?

BUT you need to take care about any software if you are using a general purpose computing device (Mac, PC, Phone) as they can "process" the stream.  I think that I have read that Roon can do DSP & volume management which will affect the sound.

Yes except not just on "general purpose" devices.  All streamers use software and with DSP anything is possible, FBOFW.

I use Roon DSP extensively with both general purpose and dedicated streaming hardware devices.  I apply DSP in Roon primarily per room, regardless of what device is doing the streaming.   DAC, amps, speakers used also factor in, but not so much streaming source device.  YMMV, it can also depend on specifics of DAC used and connection type between streamer and DAC, but use of asynch USB from most any good quality, mainstream, modern streaming device (Apple, Windows (with dedicated WASAPI configured for use), Android, others) to a good quality modern DAC pretty much resolves that, as verified by recent listening comparison tests I have done with various streaming devices as the source into several good quality DACS. .

@retiredaudioguy 

Looks like you have taken steps manage power and stray noise.  If you are curious about trying a different device between the wall and your gear, the Vinshine Audio x Kinki Studio Taihang Power Enhancer mentioned by @tyray above has been very positively reviewed by several established audio reviewers, who like tyray also ended up replacing more expensive devices with the Tai Hang.  It only has 4 outlets, and I haven’t tried it myself, but it doesn’t cost an arm and a leg, and seems to get very high marks from users.

kn

@knownothing Thanks - I'll look into that.