Will Homebrew installations, root password, hidden users, etc. carry over with Migration Assistant? or with a Time Machine backup? or something else?
Unfortunately, it does not necessarily not transfer what you tell it not to transfer, nor does it for what you do tell it to transfer for that matter. I told it to exclude one of the users, and that was honored. However, I told it not to transfer certain folders, but it did that anyway. I told it not to import printer settings, but it did that anyway. I told it to import network settings, but it did not regardless. I did have to reconfigure the Root User, but the rest went well… except that a bunch of things went wrong toward the end but I wasn't around to see what they were at the time, so when I noticed the alerts that disappeared the moment I saw them, I became worried. Not a big deal, really. All seems to be operational.
Homebrew transferred just fine, too, btw.
How do I know that all my system tweaks transferred as well? I'm not entirely certain (Gatekeeper will need to be tweaked again, brightness settings are different per the device, and… well, practically everything under the Security &amp; Privacy settings did not transfer [successfully?]), but I had no trouble finding what migrated successfully… at least, I had less trouble when Spotlight finished caching the entire hard drive because apparently it didn't transfer that useful data.
Ironically, it even brought over the broken stuff. Two remnants from my time trying to get Avid Media Composer to work (question mark icons in my Dock, which is still pinned to the right side of the screen like it was on the other device). Probably the most hilarious and frustrating flaw it inherited is my DNS-VPN-Proxy-WiFi-internet-related problem– on which I shall seek answers next.