They are supposed to be harmonized when they co-exist. I know of one example where they aren't, for very specific reasons, but haven't really been able to establish any regulatory support for that particular case.
Every new PAPI in Oz is not harmonised with the ILS (meaning the ILS TCH is different to the MEHT), because they are "eye-aligned" for long-bodied/large aircraft. When on the ILS GS, the pilots should therefore see two whites and two reds on the PAPI. For example, GS TCH is 50ft, PAPI MEHT 64ft.
YSSY
If you are in a littly where there's not much difference between eyes and GS aerial, when on the GS, you may/will see less white and more pink/red because your eyes are below the PAPI path.
Some airports seem to publish the meht, some don't.
Every Oz medium/long runway that has a PAPI has published the MEHT.