https://www.androidauthority.com/youtube-reportedly-slowing-down-videos-firefox-3387206/
Users are reporting that YouTube has begun adding a five second delay when loading a video on non-Chrome browsers like Firefox. Read on!
Pixel 2 XL, also no issues or even any noticeable deltas between Chromium based browsers and Firefox.
I'm using Fold 5 and can tell a difference in scrolling performance between Samsung Internet and Firefox. There are also some issues regarding how the UI handles transition between folded to unfolded and vice versa.
This is a known issue
Pixel 6 and Samsung A45 here Firefox is so fast I never had a complain or needed to use chrome or Samsung browser
Pixel 7 Pro on GrapheneOS
No issues. Been using Firefox on mobile and especially Linux since ever