So ive been reading around and saw that the roller width is the same between 9 and 10 speed chains. AND the cassette teeth width is the same between 9 and 10 speed cassettes. The only difference is the outer width of the 10 speed chain being narrower than the 9 speed since another cog is squeezed into the same space. Does this mean that a 10 spd chain could be used on a 9 speed casssette, obviously not the other way around.

Im already running a 10 spd crankset...would it make sense to pick up a 10 speed chain? or is what I said just BS haha