Today I learned that there's a documented performance study that was published in August 2020 about tagging in vSphere.

I found it because I was working on a tagging strategy for a customer and wanted to reference something in VMware's documentation. Google found it for me.

https://www.vmware.com/content/dam/digitalmarketing/vmware/en/pdf/techpaper/performance/tagging-vsphere67-perf.pdf