You can find a number of tutorials within the documentation! https://ccgtoolkit.wordpress.com/documentation/ . This will run you through the basics, but unreal experience will definitely help you along the way. Feel free to reach out to the support email address if you are unsure of anything and I can get back to you with some details and direction for any questions you may have.
I had thought about something similar in design, and this was one of the reasons for some changes in the latest toolkit update. Player controllers are only replicated between the owning client and the server so other players would not have access to the bool. The answer for this was to hold references to each players cards in the game state which is replicated. Thankfully this is really simple now and you can call “GetBoardState” from the game state, pass in the opponents player index, then get the length of the array from the opposing player when calling the card interaction. You can alternatively have the game state use your bool example instead of the player controller and this should work all the same!