Hi,
You can find link between release group,release class with release strategy and all its related vital release value in characteristics in t.code:CL20N /CL24N.
You need to give authorization to Releaser(user) for a release code with release group and release strategy for a characteristics with authorization object of that characteristics by allowing a value of that characteristics.
Discuss with Basis consultant & restrict Releaser(user) by authorization object for your characteristic by creating a role in t.code:PFCG and assign that role to Releaser(user) in t.code:SU01
Regards,
Biju K