My 2 cents.........
The other Steve is quite correct in that there is a large difference in the way perfectos are capped. Even the word "perfecto" doesn't have 100% consensus in its meaning to makers.
I caution, however, when clipping a true perfecto, be very conservative or you may discover that your cigar wrapper begins to unwind at the head. If you don't clip at all, and the cigar is even slightly high in RH, you'll find that the cigar smokes hot and bitter, and a nasty mass will accumulate around the cap.
All you really want to do is remove sufficient wrapper so your cap opening would be about the size of a punch cut.
Regarding all shapes...I am often surprised at how large a cut is taken when others cut their cigars. I see people taking a quarter inch off a cigar and then wondering why it unravels.