Same for Firefox on Linux btw.
BUT, I am also using uBlock Origin with Javascript blocked by default. This makes a huge difference.
Otherwise the current Firefox mobile is considerably slower for me than Chrome, especially on uncached sites. Haven't tried Preview yet.
More recently it also stopped crashing with a lot of tabs "bookmarked" (and does not loose them on a crash).
I'm a lot less interested in the mechanics of using F-Droid than I am in the no-malware guarantee that F-Droid effectively provides.
PS: I just checked - uBlock is available in Preview, woohoo, I can try it more now :) . Strange that it is the only addon available in my app, no NoScript, Badger and HtttpsE there (latest version).
On mobile, for example, I sometimes get blank pages when trying to visit a website and it will stop working until I restart the phone (internet is good because any other browser works). It is very rare to happen but it does.
Also good luck tapping on a small link in Firefox mobile, tap targets are bigger in Chrome than in Firefox.