It does not hurt to measure the journals with a micrometer for sure. Here `s a thread about the measures:
https://rennlist.com/forums/996-forum/1089034-m96-3-4l-crankshaft-journal-measurements.html#post15250757
Plastigauge is fine to give you an idea whether the clearances are ok and even at each bearing. Check the thrust bearing and the endfloat too. Also, when you do plastigauging make sure you tighten the 12 bolts in the correct sequence and to the correct torque.
Boxster
Threaded Mode
