As I try, and add a "User Field", I see the option "SQL" and "Non SQL" What are these? If I want the field to be displayed when admin checks members detail selecting "Non SQL" will work?
It is mostly internal stuff and you can do not care about it. SQL field saved in table user as additional new column but Non SQL saved in separate table. IN both cases admin will be able to check it and modify if necessary. Also you can change type of field at any point later if necessary.