I have this golfer animation. It is quite smooth movement ant the best I can find in golfer animation. But its movements are always the same pattern. For example, if I like to use the model to represent real person's movements outside in playing golf. Is it possible? That means, can I control the club's 3D position and orientation in animation from script?
You could use Inverse Kinematics (https://docs.unity3d.com/Manual/InverseKinematics.html)
With this you attach the hands on the club and move the club as you want : The hands / arms and close bones with follow it in a "realistic" way while the rest of the body will be animated as usual.
However the club movement will need some work to get a nice feeling like your original animations.
Target Matching (https://docs.unity3d.com/Manual/TargetMatching.html) could be useful too or even better but I never used that.