Multiplayer variables (or structs) Setup

Hi, could you please tell me what is the best approach for the storage of variables (or structs)? I am involved in the development of a Multiplayer RPG, with many levels, screens, maps, log-in etc and I want to answer these questions.

  1. Is the Game Instance a good place to store the character variables (or any other variables)? will these variables keep their values (level,experience, monsters status etc) through the levels and after the save and load of any players progress?
  2. Should I use Save approach storing the variables into save file?

Thank you in advance!