[YaBa]

1. Mega

2. Copy / Paste

3. Close your eyes and believe that they do it.

Jokes aside, I've moved from Dropbox to Mega; I don't store private information on cloud services, however, some particular stuff was overwritten some times and deleted the history before closing the account.

Before that, I was suspicious too of Dropbox opening files, so I've planted a canary and never was triggered, so, there's that, unless you're some VIP, I highly doubt they check your files.