I keep seeing people complain about scrolling on Firefox on Android, I've been using it for several years on Nexus 5X, I just don't see what people are talking about. Whatever you're experiencing, is it really bad enough to justify using a proprietary browser? Do you have any clue what the browser or that built-in ad blocker are really doing? Where do they get their block list? Does it block trackers? Do they collect data about you directly? I don't have time to dig into it now, but I remember hearing some kind of story about them acting as a proxy to accomplish the ad blocking, if true, that's a horrible trade-off.