According to https://bugzilla.mozilla.org/show_bug.cgi?id=1502392, browser.urlbar.autocomplete.enabled pref is no more used in Firefox 65.
So you can’t set below pref to false to disable the annoying Firefox address bar/url bar popups.

browser.urlbar.autocomplete.enabled
browser.urlbar.suggest.bookmark;false
browser.urlbar.suggest.history;false
browser.urlbar.suggest.searches

The only way to disable the popup is to use userChrome.css to control Firefox User interface.
Add below line to userChrome.css, done.

#PopupAutoCompleteRichResult {
	display: none!important;
}