See my comments on number of cores above—basically, the bump to 12-core is a big bump for $1k. 16-core is a decent bump, but of course depends on if you really would even use the difference, though it's also a hedge against future needs (or you could just leave room for upgrading the CPU to something even higher when they are cheaper, from 12 or 16).
Noise: It's so dam quiet. I mean, it's not even there. This alone is worth thousands to me. Maybe it shows up on heavy video crunching, but for DAW use, I expect it's going to remain quiet.
Video card noise: The Apple options are MPX, so no fans on any. At some point you're using more power and potential for the fans moving more, but for 580X vs W5700X, I don't think there is any consideration for noise. (I have 16-core with W5700X. I do some video work to a smaller degree, $600 was worth it for the big step up.)
Cores again, versus plugins: Well, I'd expect most DAWs to be good about using cores, so for plugins, cores are a bigger win than single-core speed. My worst-case is Zynaptiq AdaptiVerb. I couldn't run it on my 2009 Mac Pro 8-core at any buffer size. So yes, there single-core speed would have made a difference, as long as it was a big enough bump. But you're not going to run into that on the 7,1. I can run a couple of instances a core with room to spare at 128 sample buffer. And I can keep opening more because I have more cores. Waves Grand Rhapsody was my other edge case—much less cpu than AdaptiVerb, but I'd want 128 buffers to play it without too much lag, and it would often glitch when I worked the sustain pedal (especially using Digital Performer, not so bad on some others). Now it's a modest sliver of a core, not even a consideration even with 64 buf.
Also, remember the 8-core has slower memory access. For DAW/plug-in use, I think 12-core is a significant step up from 8 all around. If you're cost sensitive, I think 12 is the sweet spot, and I don't think most people will see the difference between that and higher. (But if another $1k isn't too much of a burden, why not have more under the hood?)