When I open an (existing) article or menu item in one of my sites, it takes some time before they opened. In case of opening an existing article it is about 20 seconds; menu items open after about 7 seconds. When I save or save and close an article there is again a 20 seconds delay. Saving menu items does not cost extra time.
A few weeks we replaced our CentOS server to a Ubuntu server with PHP 7.4 (instead of 7.1 on CentOS) and before the upgrade the delay was even 4 minutes.
When I turn off "Better Preview", the delay is gone. So I was wondering if you can explain the delay and if possible find a solution. FYI: I don't know if this makes any difference, but we use SP Page Builder on our site, including the Editor Plugin for SPPB.
Better Preview tries to cache the sef urls and their original non-sef urls. Which it needs for the extra info.
But this should not take any longer than 1 normal frontend page load. So not sure what is causing it to do take so long on your website.
Try purging the Better Preview cache (via the Better Preview system plugin settings).
If that doesn't help, can you reproduce this on a clean setup without all the 3rd party extensions you are using? If not, try adding stuff one-by-one till you see the issue...