Unless you have lots and lots of development time to spare, just save what you need.
Load/Save steps:
When loading, you can never re-create a MonoBehaviour or ScriptableObject instance directly from JSON. The reason is they are hybrid C# and native engine objects, and when the JSON package calls new to make one, it cannot make the native engine portion of the object.
Instead you must first create the MonoBehaviour using AddComponent() on a GameObject instance, or use ScriptableObject.CreateInstance() to make your SO, then use the appropriate JSON “populate object” call to fill in its public fields.
If you want to use PlayerPrefs to save your game, it’s always better to use a JSON-based wrapper such as this one I forked from a fellow named Brett M Johnson on github:
Do not use the binary formatter/serializer: it is insecure, it cannot be made secure, and it makes debugging very difficult, plus it actually will NOT prevent people from modifying your save data on their computers.
If you’re concerned about the user ‘hacking your save files,’ or ‘cheating in your game,’ just don’t be. There’s nothing you can do about it. Nothing is secure, it is not your computer, it is the user’s computer. If it must be secure, store it on your own server and have the user connect to download it.
Anything else is a waste of your time and the only person you’re going to inconvenience is yourself when you’re debugging the game and you have savegame errors. Work on your game instead.
Remember, it only takes one 12-year-old in Finland to write a script to read/write your game files and everybody else can now use that script. Read about Cheat Engine to see more ways you cannot possibly control this.