FreeBSD, as an OS, does not change that much. It's not hard to keep up. That's why it's such a solid OS. The main web site lists any changes or additions with each release.
https://www.freebsd.org/releases/
But you are running 16-CURRENT, which is the development branch not suitable for production or daily use. Is that why you are struggling?
AFAIK the netflix CDN boxes all run -current (they used to at least), so is the main pfsense release.
-current is definitely ok for production
No not all. I’m only on 16 for RDNA4 support, might go back to 15 once it’s back ported, if I can be bothered.
The command I referenced is not, I guess 16 only. Other examples are the service command just appearing, etcupdate being preferred to mergemaster, whatever the current preferred flavour of port upgrade tool is (poudrire, portmaster, portupgrade, something else(?)).
I also have no idea what is a sane way to do things that Linux does as systemd user services like pipewire, xdg-sessions if I want to share my screen.
I think for etcupdate etc, you should be able to get that info from /usr/src/UPDATING
For port upgrades, I dunno if it applies to CURRENT, but pkg seems to work?
I usually read the release notes for each release, which keeps me up to date enough.
I dunno about your session question. In X11, you could drop those in .xsession, but Wayland is a just a protocol, so who knows.
Yeah pkg is fine if you’re using prebuilt packages. I don’t think it builds ports with custom configs for you from /usr/ports. Or maybe it does now and I missed that too.
I much prefer sway as my desktop, but each to their own.