I found this thread during a search for exporting to Blender and saw that you had experience working with ArchiCAD models in Blender.
What are your export settings and are there any add-ons in blender that are useful for the importing and/or cleanup of the model?
Go for an NVidia RTX rather than GTX,
If you buy a GeForce 2000-series or 3000-series card, it will be an RTX card (raytracing supported by the hardware). If you buy a 1660, that will be a GTX, which does not support raytracing. Everything before the 2000-series does not support raytracing.