For anyone else who stumbles across the thread, this is from my email exchange:
There were some recent changes to how Universal Autofill function in 1Password 8 for Mac, which can cause the app to sometimes get stuck in a continuous workload and have high CPU usage. The good news is that the team have already created a fix for this issue and it should be released in the upcoming nightly and beta builds of 1Password 8 for Mac. Since the release of 1Password 8 for iOS and Android has taken priority over the last few weeks, the next beta builds should be released either be later this week or at some point next week. In the meantime, you can quit 1Password either from Activity Monitor or by pressing quit from the 1Password icon in the menu bar and it should stop the high CPU usage you're seeing.