K1r4Production

I'd suggest Ryzen 1700. I'm using it right now in my new PC for mixing sound and music in Ableton (and few other DAWs, occasionally). 
Since x299 is a high-end platform (not a good one), and since you have the budget, I suggest go for x399 instead, better future proofing. I'm sure one day you will be grateful for those extra PCIE lanes, even in music production. 1900x for now, and you can upgrade to 1950x later. All those compressors and plugins can be quite CPU demanding, both in number of cores and core speed. And you also need a lot of RAM for playback, as of with anything in the pros world. I owned 32GB of RAM right now, and my work is still asking for more ...  
You can see my build in my signature  I'm a mixing engineer btw (humbly at entry-on-the-way-to-intermediate level)

Yes. At the moment everything is fine-ish. I still sometimes have to use some small tricks to lower the CPU load in Ableton due to multiple compressors/FXs on one track (separate them in different tracks and/or use a return track for FXs, etc). I'm sure there are pro-level mixing engineers and music producers out there have this problems even with high-end processors (10-core 6950x or even 12-core Xeon on Mac Pro), that is why they use proprietary products from Pro Tools, Roland, etc, which is extremely expensive. You can check some topics on Ableton forum about those tricks, but R7 right now is the right budget 8-core processor for my level of work. 8 overclocked cores with hyperthread are really efficient. 
 
P/S: When I bought my PC, Threadripper was not out yet, and even if it had, I was short on budget. I've planned to buy Threadripper in the next 6 months. Those extra PCIE lanes and DIMM slots is much needed. You can have a bunch of captures cards and other stuffs (extra input ports for synthesizers, sound interface devices, etc) without having to think twice!