

Following the comments and response so far, I looked around quite extensively over a broad range of linux distributions. Arch, Alpine, Debian, even Gentoo booting them up and seeing what worked and what didn’t.
I found AntiX which appears to meet many of my requirements.
AntiX as a base install comes in at under 2GB HDD and 300MB RAM. By using lighter desktop environments I can push this down even further, admittedly sacrificing some usability.
It does not, sadly, have access to the AUR as it is Debian, however, there is the Sid repository, which I guess will have to do. It comes pre-loaded with RSync, LibreOffice and Firefox (which I will be booting shortly).
Even with the base of 300MB, I’m not sure I could manage to run Whonix through it, so I’m going to have to look at a different method to achieve my goals. If you have more RAM, this would be idea.
It’s in my pile in case AntiX falls through, it weighs in at only 300MB RAM base install.