Greeting! Some notes, see if they make sense:
5700X3D
The 3Ds often show no benefits in a development environment. On the contrary, outside gaming, they generally perform worse than the non-3D variants; by a somewhat negligible factor, though - only worth considering if you must squeeze every penny and every ounce of performance.
MSI VENTUS XS OC GeForce GTX 1660 Ti 6 GB Video Card
Do consider something a bit newer, this GPU stands out. Look for one with no overclock (you want stability), aim for minimum 8GB vRAM. Perhaps you can get your hands on a used 3060 12GB vRAM?
Western Digital Black SN770
A big red flag atm but you’re getting Win 10, so no flag. 
be quiet! Pure Power 12 M 750 W
This system does not need 750W PS, 550W would be plenty sufficient. Perhaps that’s where the GPU budget can be found?
165 Hz Monitor
If this is for development, then it’s utterly unnecessary. How about 2x IPS screens that can actually reproduce colour accurately?
around $1500
Excluding $300 for the screens (eyeballing), how did you arrive at $1200 with this setup?