Which file system should I use for an encrypted root partition on Linux for a single disk?

I typically use LUKS + ext4.

I've also used encrypted BTRFS and ZFS (with ZFSBootMenu) but never worked with them to any extent beyond getting them setup. I see distros such as Fedora are now defaulting to using BTRFS.

For a Linux install on systems with 8GB-16GB RAM and a single disk (no RAID), I'm seeking some advice: Should I stick with ext4? Or use BTRFS? Or ZFS?