NVMe SSD with at least 500 GB of space. Reading and writing large GeoTIFFs or spatial databases is significantly faster on an SSD than a traditional HDD.
GIS processing is largely single-threaded for many core operations (like calculating geometry or rendering a map canvas). While QGIS can utilize multiple cores for specific background tasks (like rendering multiple map layers simultaneously), raw clock speed is often more beneficial than having dozens of cores. qgis system requirements windows