Glad you like the new DAW, Eric!
The advantage of a custom machine is just that (custom):
You have complete control over exactly what's installed... and exactly how it's configured (top to bottom).
ie: Many off-the-shelf systems have motherboards with minimal settings (to ensure novice users don't foul up their machines). There are certain parameters in the BIOS that affect DPC Latency.
If those parameters aren't exposed in the BIOS, you have no means of tweaking them.
IOW, You won't be able to achieve the lowest possible (most consistent) DPC Latency.
There are also parameters that affect CPU speed (throttling). If those parameters aren't exposed, you can't tweak them.
The more you push the performance envelope (especially at ultra low latency), the more significant things like this become.
In any scenario (racing, computers, etc) where you're looking for absolute top performance, you're working with custom solutions. You build exactly what's needed... and configure it for maximum performance for that particular application (nothing more and nothing less).
A computer is like any other piece of music gear.
Some folks are happy playing Squier/Epiphone guitars.
Some folks want to play American made models.
Other folks prefer higher-end instruments like Fender/Gibson Custom Shop or PRS.
I'm (of course) biased
, but I would liken our machines to PRS guitars.
You don't need to swap out the bridge/tuners/pickups, file the nut, or level frets to have a top-notch guitar.
When it arrives, you make minute adjustments to the action... and you're ready to go.
Does everyone want/need a PRS? No
For some folks, the attention to detail and performance are worth it.