Pass variable between pages? Best secured ways

Hello folks!!
I have been trying out of lot of things with appgyver. And after almost completion of my development, I am pondering on a very basic question. What is the most secured way to pass variables to another page. I have been using page params. But lately, I am worrying if that is better or it make sense to use app variables. Specially, for passing document name of firestore.
Please provide your suggestions. Also, is there a way to encrypt this and then decrypt. Will that be worth the trouble ?