I have been running an engineering consulting firm that I started in 1990 for 28 years after being VP of an ENR 500 consulting firm for several years. Started building our own boxes from the get go as the market didn't have anything at a reasonable price. The nice part was ... what was great for CAD, is great for gaming, so after hours, we'd have everyone still in the office playig Doom. Have been building CAD PCs for over 25 years. The thing is you already know how to build a CAD workstation as the best thing for gaming if the best thing for CAD.
1. AutoCAD is barely multithreaded, as are most structural analysis programs. In our office, we actually even still use a DOS program for structural framing analysis. If you ever heard of 4 Seasons Greenhouses, we designed all their product lines on this program back in the 1980s. However, if you doing engineering and drafting , you are also writing specs, looking up product information, running spreadsheets... in other words, significant multitasking, albeit with very small loads. The clear advantage here is the Intel i7 series... and in a big way. Workstation CPUs have no relevance here and yes overclocking has significant impact. Ryzen, Xeon ... wrong tool for the job. Look at AutoCADs system requirements and it's clear that extra threads provide no advantage and the lack of speed which would otherweise be available on the 1st 2 cores hampers performance.
https://knowledge.autodesk.com/supp...t-for-multi-core-processors-with-AutoCAD.html
2. A decent MoBo... just ignore H and B cheap series boards and stick with Z. The guy is making a living here, don't go cheap to save $20. In addition the on board LAN subsystems are usally 2nd rate and in the engineering office, you are either using or backing up to networked storage.
3. Unless you venture into 3D Modeling of say cars or buildings (typically the province of mechanical engineers and architects) a Quadro is a waste of money and will severely impact performance. For 2D and 3D CAD, GTX is where its at. I have yet to see a rendering box in a civil engineering office, tho may soon be building a 2 systems in same case box soon for just that. 8700k / GTX 1180 for CAD and Intel workstation CPU / Quadro for rendering. Toms Hardware has some good comparisons of workstation cards .... the later do great in SolidWorks, Maya and other rendering apps (make it look pretty for the CEO) , but don't match up well up against GTX for 2D and 3D work
4. Memory isn't a big concern unless doing 3D modeling of structures, not the povince of the civil engineer. Even when we do cut and fill analysis, memory is not a constraint with typical projects . Of course if you are doing terrain modeling for the entirety of Disneyworld, you will need to do something special. 2 x 8GB or 3000 / 3200 CAS 15 or 16 will do just fine in most instances.
5. AutoCAD used to be rather sensitive to storage systems. Back in the day (1990s) , investing $1,000 for a 1 GB SCSI 10,000 rpm drive was the proverbial a no brainer. That's less true today than it was in the 90s. Still, we use a 250 or 500 GB SSD for OS and programs..... all data (CAD files) are stored on SSHDs. CAD files can get rather large and the typical usage patterns in the office are rather consistent. File usage is such that employees tend to work on the same projects day to day .... as one project completes, another one is begun and rarely is anyone working on more than two or three projects at the same time. These tend to remain in the SSD portion of the SSHD and as one project tails off, the next one takes its place on the fatsest part of the drive. Avoid anything that isn't at least 7200rpm and doesn't have a 5 year warranty. WD Black, Seagate Barracuda are OK but SSHDs are more than 50% faster. Be sure to avoid any drive with firmware designed for other purposes.....no NAS drives, no surveillance drives, no green drives.
6. When "making a living" is involved, I insist on top tier PSUs and cases with top end cooling. Haven't had a single component die in 7 years.
In short, you already have enough familiarity with gaming components to make building a 2D / 3D CAD system a breeze. Pay a bit more attention to storage than you normally would