Honestly? For that limited use, there's really no need to switch.

However, if you're willing to do a little extra effort, Join, by joao apps can do what you're wanting. The notes is easy as pie. Sending files to your own devices is easy. Then you just need a different file sharing method for others.

It's not a 1:1 replacement, obviously, but sending files via email, or other methods, when it's only occasional isn't something that needs to be part of a messenger service that you aren't primarily using for messages in the first place. Keeping all your eggs in one basket isn't always as good.