Need Help: Proper FH Sp Stroke and Coaching "Service"

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Good day,

(Correct me if im wrong for the statements below)

Hi, I transitioned into SP FH for a few months now. Im currently using stiga royal.
I want to grasp the science/Logic behind the SP FH technique. Vs Topspin/Block/Chop/etc.
Due to small resources available online about the SP FH, i cant get an Image in what an SP FH supposed to be and I need your help.
After asking a lot of people in my Club, some recommend a long stroke (Mattias karlsson, IMO) or a Short one (Wang zeng yi,
Accdg. to the video above, Wang zeng yi mentions that it is all in the elbow? No more waist turns? . and i am confused :( if you can give me some advice i would really appreciate it.

and i have been helping a child recently with his training. he can do the basics with footwork but his service is bad. During game play, he would always serve long balls to initiate rallies only because serving short only gives out no spin. it seems, he is having a hard time brushing the ball during service . How can i help him out.

Greatly appreciated :eek: