Advice on new build for Photoshop + Multitasking

The analogy has always been:

RAM = fast access cache.

Scratch disk = main memory.

Photoshop memory management is a dynamic process, where things are moved in and out of RAM as needed. But the scratch disk is the bank where it's all deposited. It has to be there.

The faster the scratch disk, the less important RAM becomes. 16GB should be plenty. But depending on how much multitasking you could consider 32.

I stopped building machines years ago.  I buy Refurbished Dell Workstations for around 2K they  come with a three warrantee I currently have three.  One failed within the first mount of usage. I called Dell we diagnosed the problem was the motherboard. Dell was in my house the next day and replace the motherboard. The Dell I'm on now is 6 years old and its quadro 4000 was start to have hardware issues this year. So I replace it with a refurbished Quadro K2200 from Amazon $150.

You can also expand these machines add SSD, RAM etc.  I keep all my DATA on external 4TB USB3 disk.  In the future It will most likely be external SSD where my data will be.  Here Is an example $2K system with in house service and installed legal OS Why build and service one yourself. They are easy to put together but you need toe research whet work well together and you need to deal several venders for parts and warrantees. And buy an OS.  If I pay a few more dollars then a home build would cost I feel no pain Three years of home service make my life better.   I have never had a problem dealing with Dell service Its a pleasant experience dealing with Dell  Support

Officially Adobe is pushing but I would not touch them myself... It should not matter what you get mate

https://www.adobe.com/creativecloud/hardware-upgrade/special…

Photoshop can be a resource hungry application and how you configure your Photoshop Preferences can increase its appetite. If you use scripts and action the batch process image resources can become tight.    My machine has 40GB of Ram   and I allow Photoshop to allocate up to 90% of my Ram in Photoshop Preferences Performance.  Usually I do not see Photoshop use more then 10GB. So I would thing for most 16GB of RAM is good for running Photoshop.  However, I have seem Photoshop use 30GB of Rams.     Photoshop also uses Scratch space to to supplement RAM usage.  So more then 16GB of RAM is not required RAM usage will be paged to  to scratch space.  Some thing like History states are very expensive. Each state records the document current state. More or less a copy of the document.  If you keep may history states for each open document  that can consume lots of Machine resources and I could see Photoshop page many document stated to scratch space most likey  you will never use them so performances will  only suffer if you do backup far in history.

Where I usually see Photoshop use less the 10GB of  RAM I see Photoshop use way more Scratch space  I have seen Photoshop use 120GB of scratch space.   If you do not have 100GB of Free Space on your Boot disk you do not want you Boot disk configured as Photoshop First scratch disk in your Photoshop preferences which is Adobe default setting.  Photoshop will fill its first scratch disk before allocating scratch space on other scratch disk.  You Need to have free space on you boot disk for the is where your OS and Application use for Temp Files and user Application data.  You systems performance will go to pot if your boot disk get filled.  Scratch Space is very important and for best performance should be on SSD.

The most crucial component for Photoshop is the system drive. That's where the scratch disk is - the temporary working data. You need to at least double the size, 500GB is minimum. Scratch files can be huge.

Historically RAM used to be the most important component, as a fast access cache for the scratch disk's "main memory". But that was back in the days of slow drives. The new PCIe M.2 drives are so insanely fast that the scratch disk is no longer a bottleneck. But you need to have enough space on it.

Photoshop moves large amounts of data around, much more than can be held in RAM. You never have "enough" RAM, no matter how much you put in.

I'd also swap the GeForce card for one of the entry-level Quadros. GeForces are gaming cards, with drivers optimized for the latest games. Quadros are optimized for graphics, 3D and CAD.

EDIT: I posted before I saw Trevor's post. Interesting that we both used the word bottleneck regarding the scratch disk. But it's a pretty precise description.

Good choices.  CPU clock speed is the biggest factor with Photoshop, and the 9700K is second only to the 9900K for Photoshop performance.    Check out this Puget Systems article to see how those  CPUs stack up.  

https://www.pugetsystems.com/labs/articles/Photoshop-CC-2018-Core-i7-9700K-i9-9900K-Performance-1248/

Puget  Systems is the go to place for real life, content creation, hardware information.

https://www.pugetsystems.com/all_articles.php

Photoshop does use the GPU for quite  a few functions, but you'd get no benefit from going crazy.  I  recently swapped a GTX970 for  an RTX2070 in my i9-7900X system, and saw no noticeable difference in Photoshop performance, so the GTX1050 Ti will work well for you.

NVMe drives are a good choice.  It would  be good  if you  could fit a second one, and  use it as Primary scratch space,  but if you  are careful about how use use the boot drive, you could keep that as your primary scratch drive.    You only mention the one drive  though.   Will there  be other drives for data storage?

16Gb is OK for memory, but try and OC it if the MB will let you.  I have 64Gb RAM, and still see some pretty big temp files on the scratch drive.  I am sure that reading and writing to and from scratch drives is an important bottleneck with some systems.

I have no idea how  hot the 9700K runs, and what cooling it needs, but a 4.9GHz suggests it needs taking seriously.   I just  checked its TDP, which is only 95W,  so not too terrible.  I'd say that a 240mm liquid system will be fine.  Where will you mount the radiator?  That's a  nice roomy case, so  you'll  have options I'm thinking.