Hmmm... I've dealt with this issue consistently since I started using Vectric 4-5 years ago. This was one of the prime reasons I upgraded my 6-year-old MacbookPro - I would tell Vectric to simulate or recalculate toolpaths and it would slow to a crawl. I'd be forced to walk away for several minutes (which would turn into an hour because I'd get busy on something else - killed my CNC productivity.)
I lied / forgot. My Mac only has 128gb of RAM but it's upgradeable to 256gb.
(Personal rant: When in doubt... Buy all the RAM you can afford... This has been the most important factor in computer speed for all of my 30+ years in computers. (Yes, I'm old. I was a beta tester for Windows95.))
As someone stated - most of the machines out there have 16gb or less of RAM and 1-2 CPUs. But I've always dealt with this problem - across 4 different computers. (2 Camaster CNCs (Stinger and Cobra) and their associated dedicated (slow) PCs and my old laptop and now this new desktop Mac.
Attached is the CRVD3 file, etc. It a tiny, simple file... I cannot imagine why it was so slow... Again, in this particular instance this did not happen when I first told it to simulate. It was only AFTER the toolpath was previewed once (and we did not apply "Reset Preview) and then my son (who is just learning Vectric) clicked "Preview All Toolpaths". I'm tempted to back off on the Parallels settings so I can recreate the problem exactly but I simply don't have time. If Vectric wants me to prove/confirm/verify later I will do so...