Comparison between Mailcow and Mox:

Mailcow (from https://docs.mailcow.email/getstarted/prerequisite-system/#m...):

  A single SOGo worker can acquire ~350 MiB RAM before it gets purged. The more ActiveSync connections you plan to use, the more RAM you will need. A default configuration spawns 20 workers.
  *RAM usage examples*
  A company with 15 phones (EAS enabled) and about 50 concurrent IMAP connections should plan 16 GiB RAM.
  6 GiB RAM + 1 GiB swap are fine for most private installations while 8 GiB RAM are recommended for ~5 to 10 users.

Mox:

I checked with htop, and my Mox process currently takes <100 MB.

Manually - I want as slim/minimal/resource-efficient a setup as I can, and to understand what I'm configuring.

https://workaround.org has pretty good instructions for each component that allows one to understand things: very little magic involved.

* https://workaround.org/ispmail-bookworm/big-picture/