I believe that CPU is the 9th gen Intel Core i5-9600k, which should be able to run basic Cubase projects just fine with a limited plugin count, but there are plenty of third party plugins that will bring it to its knees, unfortunately. The i5-9600k was released in 2018. It can’t be expected to perform like a modern CPU. However, it will run basic Cubase projects.
Staying within the Apple ecosystem, even if you ran out and bought the cheapest base model Mac Mini M4, it would technically be over 2X more powerful. And a Mac Mini M4 will probably “feel” even more powerful than that, especially if you are running all Apple Silicon apps and plugins. I no longer use Macs so I can’t help you there though. (I transitioned back to Windows recently.)
A very good audio interface for the money, punches above its class for sure. The performance/latency is also good, both on Mac and Windows.
Agreed with pretty much everything @Thor.HOG said. No need to run it that high TBH with they way Cubase is engineered now.
My suggestion would be the following:
1 - Consider upgrading your computer. I know, I know, it seems like throwing money and hardware at the situation is what a lot of people say, I get it. But Apple really has moved on from Intel! A lot changed in the last 6 years, and even back in 2019, the i5-9600k was not a very powerful CPU. Apple Silicon is now on the fourth iteration since then, and it’s really quite good. I’m not a fan of Apple, but I definitely respect their hardware accomplishment. The M1 - M4 are impressive for performance per watt. You’ll experience a big improvement to the whole user experience in general. Intel i5-9600K is showing its age for sure.
2 - If you MUST stick with the i5-9600K for now, then it will work fine for basic projects with limited plugins. But it will easily spike depending on what and how you load plugins on tracks and buses.
I would personally do a completely fresh/new installation of MacOS from the ground up, and start over with the most basic configuration of your DAW software. I do this from time to time, and it’s amazing what a clean install will do sometimes. I’m not saying it will solve your problems, but if it’s been a while since you did a fresh install of the OS, then maybe consider doing it now. (Make sure you back up all your important files before a fresh installation of course!!!)
I would then Install Cubase 14 and create a simple test project with only the Cubase plugins at first and see how it performs/behaves. Keep the MOTU at 256 or 512 latency, and use the default settings of Cubase to see how it runs. If there’s anything strange or unexpected, then perhaps someone with a Mac can help you troubleshoot at that point. But I regularly test Cubase on different hardware (no more Macs though), and it still runs surprisingly well on old 9th-gen Intel CPUs… but you have to set your expectations to realistic levels.
If a clean OS installation plus a clean Cubase 14 installation work well for you, then install your third party plugins one-by-one, very carefully, and test them one at a time by adding them to your simple test project.
If you do all this scientifically and methodically, there is a good chance you will uncover what specifically is causing problems for you.
Good luck!