The old plugin's method of opening the summariser results in a new tab is preferable because tabs can be ignored until loaded, and doesn't involve an annoying pop-up (which was everyone's least favourite thing about the old internet).
The results aren't instant enough to justify having a pop-up obscure the content. My normal use is to view a related page's summary without having to leave my current page and break my flow, which a pop-up fails at.
Please add an option to the plugin to simply open the normal Kagi.com summariser page with the given url in a new background tab.
edit: Also, you cannot switch to the "key moments" summary, which is generally more useful (and is the default via the site).