Which file sharing service is most secure? Or: which privacy method is most secure? See list

So I'm trying to find a method to send large files securely. I was using Firefox Send before it shut down, and haven't actually needed it until now. A quick search for "Firefox Send Alternatives" returns a ridiculous number of fluff articles. But it did raise the question of security/privacy because I wasn't sure which technology protected the me, my file, and the recipient's data. The three I was hoping to pit against each other are 1. Firefox Send, 2. …

file sharing privacy service sharing