You can build a similar setup with workstation board that have more Pci-e slots and 10G network/TB and well 128Ram
with the Mb I have ordered and the I9 GHz you can overclock, this Xenon is locked, so I can't recommend but I will go this way.
MasterDaw
Asus WS Rage 10G
I9 X 10core.
Pc Slaves
8core Xenon "old"
10G network/netgear Switch
10G cards Intel 550
Samsung SSD
Win 10 Pro
If you wanna find the optimum in High Performance that is not too costly for master DAW and do not use too much power then I would recommend Xenon as slaves/master who consume small amount
watts they are really stable. Master Daw with high clock speed and several core is the way to go, but if you need 18-core to be satisfied no, you can think about whether it's worth it. A 18-core I9 in full action consume up to 500-700 watt and that is not cool.
A 10/12-core with clock speed around 4GHz or higher if you have a engine room where you can cool with multiple fans/water. I will use an I9 10-core with clock speed 3.5-4.0Ghz with 2 slaves(machine room), if you go too high in Ghz it gets hot.
But what the optimal DAW design is for price and performance is hard to say. But using a dedicated computer for mixing is preferable. So to answer your question, both parts are important to a certain level of core and frequency, since I find it impossible to determine without testing what gives better results ...Daw program/plugins/softsynth how they use core is impossible to know... I have checked the core balance when mixing huge template and there are som unbalance in the core some are more used then other when there is heavy load of plugins etc.
Sorry for my bad English, I hope I can help anyway.