The main 4 BSD flavors recomended by kill9 are [FreeBSD](https://www.freebsd.org), [OpenBSD](https://www.openbsd.org), [NetBSD](https://www.netbsd.org), and [DragonflyBSD](https://www.dragonflybsd.org)
They are all good for different people, but I will give a quick explanation of what they all are.
FreeBSD/DragonflyBSD: Good, reliable desktop operating systems. DragonflyBSD has lots of interesting features that make it different from FreeBSD but the best thing to do when picking out FreeBSD or DragonflyBSD is trying both to see which one is for you.
OpenBSD: Good, minimalist, secure software. OpenBSD is good if you want a suckless and very secure operating system.
NetBSD: NetBSD runs on anything. I haven't used it much but it seems like a very nice operating system and a good BSD derivative.
I use FreeBSD and DragonflyBSD as my daily driver, because imo they are the most practical operating systems for daily use within this list, but with BSD you sort of need to try them all to find a good operating system for you.
The only BSDs I do not recommend are BSDs such as (The now-no longer developed) TrueOS, FuryBSD, etc, as they come very bloated out of the box. Using BSDs based on others is okay (OpenBSD is technically based on NetBSD, and DragonflyBSD was a fork of FreeBSD 4.x), but do not use a BSD that is bloated as soon as you install it.
The other main contributor to kill-9 (the person writing this) uses keyboard-driven floating window managers, and I recommend using 2bwm, berry, or wmutils (which isn't technically a window manager, but it's a very good way of managing windows). They are highly configurable and very good. kill-9 recommends berry, 2bwm, and wmutils for this.