Hello Dani...
in my opinion the Auto start or Manual start are not very different on the airbus A320 fitted with the CFM 56...because :
in the Auto start the LP fuel valve will open at 22% N2 (Very close to the Max motoring Value)
and in the Manual start the recommendation is to set the LP fuel valve (engine master switch) when the N2 Reaches more than 20% or reaches the Max motoring value.
and i have noticed the max motoring value is almost 24-25% N2.
Good Day.