Everyday browsing (except watching videos online which is indeed very slow) is almost seamless on my 16-year-old Thinkpad running NetBSD, even with its meager 4GB RAM. NetBSD in general is pretty chill on system resources. FreeBSD and DragonFly are not quite there, at least in my experience. I haven’t used OpenBSD for browsing or watching videos in AGES (I only use it for non-graphical applications), so I wouldn’t know.