Beastmopth Alchemist+ Master Chymist question

[Heavenfluff]

So I am aware that a Master Chymist when using mutate ability gets the effects of a Beastmorph alchemist's Beastform Mutagen ability. What I am asking is: when using the Mutate ability, does the form that the character assume always match the currently prepared mutagen? Otherwise, can the form used with Mutate have diffrent beastform abilities or allocated ability score bonuses than what the currently prepared mutagen has?

[Some Random Dood]

When you use mutate, you can spontaneously choose what bonuses you want from beastform and what stat bonuses you want.