I have a little more RAM than both of you but I currently have open - Firefox, Internet Explorer, Outlook, Windows Explorer, Adobe PDF reader, 2 x Archicad 18, 3 x Archicad 17, 1 x Archicad 15 and 2 by Archicad 12 just for good measure.
18 still feels fast and responsive as if it was the only program open.
They are all only single residences (not huge commercial projects).
All the Archicads show I still have over 8GB of available RAM (except 12 which is showing 4.0 but that is as much as it can use anyway).
Available RAM can be seen in the right hand side of the Status bar if you have that turned on.
Barry.
One of the forum moderators.
Versions 6.5 to 27
i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11