M1 Max vs. M1 Ultra

I've understood that generally, all instances of a plugin in Logic need to run on the same core. For example, if you're using a guitar-amp plugin (AmpliTube, or one of the Neural DSP Archetype: plugins) on multiple channel strips, every instance of that plugin needs to run on the same core, and when you've saturated that core, you start running into audio glitches.

But I think I might be wrong about that. Looking at the CPU graph, I'm starting to think that all the plugins on a given channel strip need to run on the same core. So if you have two channel strips, each with say a noise gate, pedalboard, amp sim, cab sim, EQ, and compressor, all of the insert effects on the first strip will run on one core, and all the insert effects on the second strip will run on a second core.

Which of the two is correct matters when deciding whether I should buy a Mac Studio with an M1 Max or an M1 Ultra. Since the CPU cores are identical on both SoCs, there would be no benefit to the 10 extra CPU cores on the Ultra if every instance of a specific plugin needs to run on one core anyway. But if individual channel strips can run on different cores, then obviously the extra cores will have a major impact on performance.

So was I right the first time? Or am I right with my second guess?