New Build — i9-7900X or Threadripper?

In all the years of using custom computer builds, I have never agonised for so long, or changed my mind so often.  The reviews and bencharks are all over the place for a start.  Puget Systems and Toms Hardware are the most reliable, and with by far the majority of my workload being with the lightly threaded Photoshop, I'd decided on the 7900X's higher clock speeds and relatively low core count.  Keeping it's temperature under control seems to be an issue.  Runing it flat out stands a chance of it getting hot enough to throttle back even with a big 280mm AIO liquid cooler, but Photoshop is hardly going to stress it.

Then someone pointed me at this video

It does not show any Photoshop benchmarks, but my thinking had been to optimise for Photoshop, and put up with a slight compromise with apps like Premiere Pro. but this site has Threadripper with a significant advantage with the higfhly threaded apps — and it does not get nearly so hot.

I'd found a nice X299 mother board in the ASRock Fatal1ty Professional Gaming i9, which has a ton of SATA and USB3 ports, and a better than average VRM with 13 phases, but I liked the MSI X399 Pro Carbon even more.  There wouldn't be much in it cost wise as the X299 MB is a bit cheaper, but I am not going to worry about a few hundred dollars either way after all this hassle.

There must be people who have built both Threadripper and 7900X systems for Photoshop by now, so if you are one of them, and read this, I would dearly love some feedback.  Especially if you have the i9-7900X and can tell me if keeping it cool is as big a problem as they are saying, and if not, how are you managing it?

Thanks in advance for any help.  I am desperate to get tis nailed down and start the build.