2) APFS was, from inception, planned and designed around the use of solid state storage only — and fast at that (direct-SATA, PCIe/NVMe, and up).
That's the surface propaganda, and any claim made by Apple must be viewed through a lens of knowing that they are skinsuit over an intelligence operation. Their ulterior goal is to surveil the user 24/7. Previously this had been done by enticing the user with a server-based cloud ecosystem; with Catalina, the OS itself would finally become fully integrated, with all app use monitored (this resulting in Spotlight Indexing and other telemetry apps going into crazy mode).
This greatly-increased amount of disk access (where previously a GUI OS' job was to interpret device input, then stand silently by until the next) was of course much quicker on an SSD. --So, how to get everyone into an SSD? Easy: design a new version of the OS (Catalina),
then make it an upgrade path for machines with regular spinner drives. Those machines will now run sluggish, and their users replace them with new silicon product restricted from the running older versions of the OS.
Now none of this increased disk churning requires a new file-system, and APFS is
not faster on an SSD than HFS+ is. (When I rag on APFS for being a disk-grinder, I'm really critiquing OS versions that require it, or Catalina+.) High Sierra and Mojave do not have any speed benefits running in APFS over HFS+, and my copious anecdotal experience suggests that its slower (if only for the additional overhead of the OS now managing a user data partition rather than a user folder).
I remember when this GUI OS booted off an 800k floppy diskette, and was reasonably snappy.
Based on my experiences with High Sierra, I would not dream of trying to run Mojave on a regular basis from a spinner,
I do it all the time: 1) Clone Mojave into an HFS+ partition at the "front" of the drive (usually a two-step cloning process), and 2) disable MRT, Spotlight Indexing, software update, and a few other pieces of telemetry in Terminal. 3) Once you've tailored your "master", you can keep cloning it to other machines with CCC5 and GetBackupPro3 -- which is precisely what I do when I pick up a 2015 i5 iMac with a 1TB spinner at the recycler; they literally run four times faster with Mojave/HFS+ than Catalina (or higher), and Mojave/HFS+ is not worse than High Sierra (which I put on 2009 to 2011 pre-"metal" machines).
3) Harvesting gets blocked sufficiently well with the robust use of Little Snitch and also the adding of unwanted stuff to the /etc/hosts file.
RadioSilence is better than Little Snitch, but neither of them thwart Apple's OS-built-in snooping, and weren't designed for that purpose. Even if all the garbage in Catalina+ could be ripped out/turned off, you're still dealing with all of its other baggage, e.g., murder of 32bit, etc.
We have to come to terms with the fact that the MacOS and Windows platforms are both now fully
enshattified, and that our remaining choice is to use the best older versions (Mojave & High Sierra), Win10) while we wait for Linux to pick up the slack.