We just released an update to the beta channel of the 1Password Safari extension that includes an "Animate filling" option (Settings > Logins).
You can switch to the beta channel of the 1Password extension by checking the box to "Allow beta extensions" on the extension installation page.
You can get to the extension installation page by selecting "Install Browser Extensions" from 1Password's application menu.
If we can be of further assistance, please let us know. We are always here to help!