Given you are using the same GPU
The stuttering / dip was probably caused by previous CPU memory controller and/or RAM being DDR4 (DDR5 has 2x bank groups, see video below) and maybe affected a bit by the frequency (also see video below for frequency effect on performance)
It’s great that these days most modern systems we can build don’t have much/any stuttering. I think I will be stuck with 2K gaming for at least 5-7 years (just switched from 1080p last year).
I saw a that a few months ago you were hoping for near silence. What I did a few months ago (when it started to get hot this spring) was add an air conditioner in my office to cool down me and my electronics. Now the computer fans don’t have to work nearly as hard to keep the system cool since the air is 20f cooler.
The owner of the apartment i live in doesn’t allow an AC on the office where my computer is since i would have to cut a bit of the wall for installation. But yeah, that would be the ideal solution. This build turned out to be the most silent pc i’ve ever had, even under heavy usage, so it’s really not been bothering me much.