As Dameon said there are no core limits enforced on management. The automatic resource and Java heap size scaling tops out at 12+ cores for a SMS, so while having more than 12 cores certainly won't hurt it probably won't provide any appreciable performance gain.
Based on some testing I performed in the past, there was a noticeable increase in SMS performance as each core was added up to 8, then only minor improvement for cores 9-12, and no perceptible improvement beyond 12. For MDS/Provider-1 however more cores beyond 12 can certainly help for configurations with a large number of Domains/CMAs.
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