Are the three kinds of conduit (PVC, standard metal and thin metal)
considered to be interchangeable?

Only to the degree permitted by your building codes. Call and ask if you have
any doubts. Keep in mind the property differences of the materials, like PVC
doesn't corrode, EMT doesn't melt at temperatures over 100 C, rigid conduit may
be overkill for your application, etc. HTH

Joe