Conjuration Spells

The DM chooses the animals, fey, or other conjured creatures unless the DMG explicitely says the player chooses. However, in the cases where the player gets to choose the CR and number of conjured figures that appear, the DM will do his best to indeed use the max CR allowed by the spell. Note that if the conjured creatures can not all fit into spaces that the caster can see, the number of creatures will be less than the maximum so that they can fit.