Hello Imogen!
Thank you for taking a look at my issue.
Regarding the leap settings, I have turned all of those off because I have implemented those optimizations on my site by myself. This got me benefits of those optimizations, while avoiding TTFB increase caused by LEAP modifying my code.
I have only enabled some JavaScript optimizations recently, as looking at performance logs of my browser clearly indicates CMP JavaScript is to blame for the bad INP. JavaScript optimization didn't hellp at all, while CSS has nothing to do with this issue, according to the performance logs.
I hope you can report this issue, together with script names I have mentioned to the dev team. Please note to them they will have to use VPN to see my website as a EU user, for the problem to show up. I also have to mention that I saw many users with the same issue in this community, so I really believe this is not related to my website.
Best regards,
Bojan