How to determine if the TSMC 0.18um PDK is OA or CDB compatible before installing it?
Nothing is mentioned in the included documentation and need to know if it is possible to just look into the files?
Yes, if you look into the technology library you will see a "techfile.cds" for a CDB-based PDK, or a "tech.db" for an OA-based PDK. Also in the cellview you would see .cdb files for CDB and .oa files for OA (for example, in a layout cellview or schematic).
Hopefully this answers your question.