Sadly your really not getting true security if your using any phone online, even if it has a VPN app. Those smartphones were built by default to track, monitor and spy on users and accumulate all data for forensics. And, remember there is absolutely NO security what-so-ever behind two-factor authentication. It is absurd in fact, the more identifying info you give out to third parties the MORE vulnerable your accounts become because they can be easily de-anonymized by any legit professional hacker or government agency.
You know what I carry? A flip phone, no internet. No, it's not very secure, but the fact is I don't use it too often, only for making calls just like any old fashion phone. It has no social media on it, no apps, no games, just a contact list of numbers and caller ID. There is nothing interesting that phone is really used for at all.