Chrome x64 can get a bit heavy in memory usage sometimes but it is very fast, very secure, and very stable. If you have privacy concerns about Google but still want to use Chrome, you could use Opera. I can't recommend any other browsers based off Chrome as Opera is the only one I know of that stays up to date with the latest security fixes from Chrome.
Firefox is also a great choice, it is a bit lighter in terms of memory, still very fast though. In my experience, it is a bit less stable than Chrome but it is still a great browser. I haven't used them but many people like Cyberfox and Pale Moon, which are x64 browsers based off the Firefox source code.
Both of these browsers have plenty of great extensions and addons, I prefer Chrome for uBlock and HTTP Switchboard but Firefox has some great exclusive ones too.