I use Firefox mobile pretty much exclusively. I haven't noticed any meaningful performance difference between it & Chrome. It also seems to perform fine on my Fedora laptop.
I don't even think its about number of tabs. Just yesterday and today, Mullvad browser takes minutes to load a set of about 7 pinned tabs (with no other tabs) on startup, whereas Helium (which is based on Chromium) loads in a second or two close to a hundred tabs.