PS performance issues high-res images, many layers. Mac upgrade suggestions.

Hello,

I have PS performance-related issues. I work with composite images in high resolution, sometimes hundreds of layers of different kinds, large files. I always get performance issues at the end of my projects when file sizes are large. I do it as a profession and the slow loading time hurts my deadlines.

After trying different solutions (see lists), I want to upgrade my system, but I want to make sure I buy hardware to make a substantial change.

Questions:

• Firstly, is there anything I can try before replacing the system to give a substantial performance boost? (see list underneath what I already tried)
• How much physical memory can PS use? 
• Will I get diminishing results the more RAM I add?
• Would it be beneficial to add a larger SSD scratch disk? (current 500GB)

I'm looking at the 2019 Mac Pro

• Is it beneficial to have higher GHz and fewer cores or lower GHz with more cores in PS? (3,2 with 12-core or 3,5 with 8-core)
• Radeon Pro 580X GB Radeon Pro Vega II 32GB

Common issues are:

1.  Spinning wheel
2.  In general long loading times
3.  Slow brushes (using the brush ques up its "brush activities")
4.  Moving layers/adjustment layers are slow
5.  Transforming layers/adjustment layers takes a long time
6.  Converting to smart objects are very, very slow
7.  Saving files takes a very long
8. Occasonaly PS craches.

Things I've tried and workflow:

• I applied many PS performance guide settings, and I've returned to the guide many times during the years to update myself.
• I upgraded my ram to 64GB
• Installed 500GB SSD USB 3.0 as a scratch disk and used it as the primary scratch disk
• I permanently save my PSB files on my internal SSD for faster saves
• I close all other software and activities that are not necessary, that takes up RAM and processor power
• When files grow too big, I convert sections of images to smart objects, making the file easier to work with. But it makes other parts of workflow slower
• Efficiency is almost always at 100% when I check
• I frequently purge cache in PS and also have software to "purge/allocates" RAM. However, that works.

My specifications:

Manufacturer: Mac Pro late 2013

Processor: 3.5ghz 6-core Intel-Xeon 

RAM: 64GB (4 x 16.0GB 1866MHz) 

Graphics cards: D500 x 2 with 

Storage: 1tb of internal storage. I also use a 

Scratch disk: 500GB SSD as scratch disk connected with USB3

I very much appreciate all comments and feedback.

Regards Andreas