Neither AC nor CineRender would utilize a second GPU.
As for OpenCL rendering in 19 or later... it would be the Maxon / Cinema4D rumor mill to check on that one... assuming that ArchiCAD will be kept in sync with updates to C4D.
😉
Between this and your core-count question... just in case you haven't read through the various benchmarks at Bare Feats, check them out:
http://www.barefeats.com
P.S. Love your signature ("Programmer dating an architect")
🙂
One of the forum moderators
AC 28 USA and earlier • macOS Sequoia 15.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB