I have these two shirasawanum from seeds taken on a shirasawanum 'Autumn Moon'. They are quite different from each other, see : Autumn colors 2020 - Maples I suspect the taller one, with smaller leaves, is a cross between A. shirasawanum and A. palmatum, look at the buds (one square is 0.5 cm) : For a comparison, buds on the 'Autumn Moon' :
