There is quite a distinction between a single-shaft turboprop (T56, TPE331, Dart, others I'm sure still active), vs. a dual-shaft or free-turbine engine (PT6, CT64, CT7, PW100 series).
You can quickly tell them apart when shut down. It the prop is feathered, it must be a 2-spool machine, because the core or gas generator can be started without rotation of the free turbine. There's no mechanical connection, but rather gas-coupled turbines. Thus the prop blades can be set for either high RPM (takeoff) or low RPM (cruise) without directly affecting the core speed.
Helos use free-turbine turboshaft engines - they can be started with the rotor braked.
On the other hand a single-shaft (single-spool) engine will always be in flat or fine pitch when shut down, because minimum drag for the prop load is necessary to get it started. The prop speed and the core speed are directly linked by a gearbox.