I looked at 28 PN last night with an 8" Meade LX90 SCT at 205x.
This was part of a guided tour of 50 PN. The rest were not up.
The Meade had them all in the high power field but not usually in the middle. No filter was used.
The aim was to rank them by surface brightness.
The results were:
Very bright (NGC numbers)
7009 6826 3918 7027 6572
Have you seen these planetary nebulae?
Do you agree with these brightness estimates?
The magnitudes do not give that order but that is how it seemed.
However it is hard to be consistent with estimates when the altitude and sky glow vary.