It is safe to delete it if you think you will no longer need it.
No need to though unless you are desperate for disc space.
All versions of Archicad run independently of each other.
You may still want to open you older files in 19 rather than migrate them to 20.
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