I am just getting to the cad drawings so the largest assembly I did so far is the bedding spreader I have as my profile file picture. The only other software I usually have open is: media player, task manager, google chrome, and file explorer. Before I put the dedicated graphics card in it was really slow.
What CPU do you have?
Usually for CAD we need the fastest single core speed with the extra cores to cover other tasks.
i5, i7 etc are good. (usually but early ones can be very slow by modern standards)
More cores are better for rendering and video editing etc.
It is actually a Dell precision 7710
I originally bought to support some heavy duty database work (SQLServer, Oracle, Centura, PervasiveSQL). One of the Oracle DB was well over 500Gb with several hundred tables. The Xeon processor performed really well. At the time, 8Mb cache was quite a lot!
If I were to spec a new machine today, I'd probably look at one of the i7 based CPU but again look for a device with lots of cache memory.