You don't need to focus on a GPU for photo editing, what you really need to focus on is RAM, CPU, and Monitor.
https://pcpartpicker.com/list/XsR3tp
Check out the link above to see a custom build list.
-- What I chose and why --
CPU: 9700K will give you best core clock frequencies (amount of tasks per core) which photoshop prefers over multi-threaded perforamnce. So AMD performs worse on photoshop.
RAM: Anyhting above 3200MHz is ideal for optimal perfomance. Trident Z being the best ram on the market right now. And you have the money to spare apparently for the best.
Monitor: You can choose any other monitor you prefer but I highly recommend a monitor that has these qualities:
- IPS PANEL (For best colors)
- Anything above or around 400Nits (this is max brightness, anything above 400 gives you HDR support, meaning true blacks and whites) though this isn't critical, 300 will also work fine.
- Above 60Hz refresh rate (The smoother you move around around your screen the better it feels to edit, this is subjective though)
- 27" screen size. The more real estate the easier it is to edit larger files. This comes from personal experience.
GPU: The 5700XT is a cheap but powerful card that will handle 1440p gaming if you so choose to play games. You don't need a super powerful graphics card though to photo edit. Even an old video card will be fine, just as long as it has the proper video output ports for your monitor.