Naomi’s advises are superb. Braxman’s I’d take with a hint of salt. They tend to have a point behind them though sometimes a bit light and he’s rather keen on selling his own products.

What data? The only thing they know is when the account was created and when was the last access.

You do need a phone number to signup to Signal but you don’t need to share it with anyone. Just create a new username for each new person you want to add.

I’m using their starter lifetime plan, and everything works flawlessly. That’s a plan where you pay only once and keep it forever.

Try filen.io. Similar concept as Dropbox but zero knowledge and encrypted. you can easily share direct (expiring (so you choose so)) links to files with or without password.