A process has a main process thread. At least on windows the gui is not guaranteed by Microsoft to be threadsafe - meaning that many threads in same process simultaneously can not write to screen. You actually can, but it depends on graphics drivers to a degree whether this causes problems or not.
Application can then run many threads for various purposes.
Threads can be distributed by OS or by developer to some degree. Developer can request one core for a thread, but don’t think that is always met by OS.
So looking in task manager in windows(don’t know mac) you can see computer running maybe hundreds or more threads one can assume one core has to deal with many threads, and how many is affected by developer detail control.
Samplers and multiinstrument synths often has a setting how many cores may be used.
BIOS(at least on pc) has setting whether to allow hyperthreading or not. That is a way to utilize two logical cores on a single physical core. Also making it more efficient than if to switch threads on non-hyperthreading enabled cpu.
So look at that many threads are running on the same core - don’t overestimate multi core and it’s importance.
But there is less overhead switching between threads(called context switches) to run a cycle(like 20ms each or so) it is an advantage.
But not like quad core run double performance compared to dual core.
But always interesting to compare benchmarks how cpu and gpu has progressed.
There is a tab for video graphics comparisons and such as well.
And looking at prices you can see what is more bang for buck, kind of.
You can see that cpu benchmark pretty much correlate to cpu clock used. A 4.2 GHz clock is so and so percent faster than a 3.6 or 2.8 GHz of the same like a i7-7700 or a i7-7700K etc.
But Xeon is most efficient, and then i7 and then i5 etc - but can give better bang for buck looking in tables.
About Cubase one interesting thing I learned on forum is that multiinstrument samplers may benefit from running multiple instances instead of many instruments on one instance. They will then get separate thread - and thereby may run on different cores etc. But have not tested how true this is and if significant or not - and under what circumstances you benefit from it.
One thing that seems good about separating instrument instances might be to render just one instrument, as needed. Think multi outs are all rendered otherwise.