Yes, NPSHa will change due to the inlet losses (friction loss) in the approach pipe work etc. Increased flow will account for higher inlet losses whereas lower flow will account for less losses, which are measured at the impeller eye.
NPSHr is not really a function of the affinity laws although they are often used for an approximation, true NPSHr figures should come from the manufacturer or tested pump performance curves.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)