Very late, but I’ll still add my 2cents.
I mainly edit on FCPX , however I’m still using FCP7 for a TV production company in NYC ( a number of major tv shows still use it, familiarity I think).
FCP7 still works on Sierra, but not on High Sierra. Been postponing upgrading my 2014 macbook pro to high sierra because of FCP7 usage.
My future solution is to partition the hard drive and just have mavericks or newer on the second partition, and just have FCP7 and maybe DVDSP running on it until these production companies switch over. They have a distaste for FCPX, so they’ll probably move to Premiere.
Ken Kozak
Principal at Kendo Media/Trios Films
https://kendo.media/