Integrated and separates for me, but where the line is blurred are integrateds with no front end gain (ie, a high gain power amp, fed passively).
If someone is using say a HK PM660 or a Sansui AU-D7 or a Sony TAF-333esr or a Sony TAF-444esx or numerous other 80s/90s amps, there is no difference between a power amp (with level controls) and an integrated with a passive volume control.
Then you have the guy with a proper (with gain) preamplifier and the guy with a (volume control in a can) passive "preamp"*.
Oh it gets complicated.
*no such thing as a passive preamplifier. A complete misnomer. It is an attenuator, or possibly a transformer. (some 'passives' with 'gain' merely use a transformer to 'step up' voltage due to the low impedance source they are fortunate enough to be fed with)-a 'passive' cannot increase the overall power of a signal and, as such, cannot ever be considered a pre-amplifier or any other iteration of amplifier.