As I noted earlier in this thread, I am also observing the slow down. I went to disable 3rd party integrations in 1Password following Peter's observation. There is no option to disable these integrations in 1Password 7 so I reached out to 1Password support. I was advised that these integrations are not used in version 8.
We made sure that version 7 wasn't installed, reinstalled version 8, then removed the data for version 7 that contains the 3rd part integrations from my system - just to be sure they weren't being used by any other apps.
So, in my case running 1Password 8 with no 3rd party integrations my macros are very slow compared to the situation running KM 10.
I would conclude that if 3rd party integrations with 1Password are responsible in some way for some people's slow downs, that doesn't explain my situation and there must be some other cause.