If I'm using a 1x32 PLC fiber splitter, and attenuation is 15.05 dB, will the beam coming in always split 1x32 and each strand will have the same attenuation whether I'm using 1 of the 32 or all of the 32? Or is there a way to have it only split to, say, 16 strands? Should I be designing a GPON network in a way such that N is as small as it can be while still allowing room for expansion?
The PLC splitter is a passive optical device, so there's no way to make it split less than it was designed for (other than to replace it). As far as I know there are PLC splitters with uneven ratios though. There are also FBT splitters that are adjustable.
Small split ratios are required for maximum reach or maximum uplink speed, short reach allows higher split ratios.