All CAD drawings and models will appear to have "jaggies" on curved edges, due to the limited number of pixels on a computer monitor. A 4K monitor should make onscreen drawings and renderings look much better.
Printed drawings should always be very sharp.
I use a 3 year old 6 core i7 with 32Gb of RAM, and an older GTX970 video card.
If I was buying today, I'd get an i7-8700k, 16-32Gb of RAM, and a GTX-1080.
This will be plenty fast, and should last 5-10 years.