PS on coats, some change, some don't, but these are very minor changes that most people would never notice and when they are more difficult -- eg a really cottony fluffy coat -- a simple thinning shears easily manages this at home or the groomers. I think the issue of coats is often more related to age and genetics and diet and overall health, rather than neutering. I don;t think age of neutering matters in this regard. I've neutered under 1 dogs and older adults. Some have minor changes, some really have nothing one would notice.
People can change coat quality more significantly by having groomers shave or trim their dog!