Depends on what you want. Honestly that tablet, while it fits what you want it for, is running a really outdated version(4.2 was released in 2012/13 I believe) of android that isnt very secure, even without having any google apps on it. if youre basically wanting a phone for just using data, i'd instead recommend getting an older nexus phone like a Nexus 5 and putting a custom rom (Android 5.1.1 or above) on it. Lollipop added lots of improved security features and better/easier encryption, so if it has that or even 6(marshmallow, which is easy to get on a nexus device) you should be in good shape.
Then you can decide whether or not you want GAPPS(all the google stuff, including the Play Store) or just want to use an open source app repository like
F-Droid, which has lots of secure chat apps like Telegram(only if you use Secret Chats, i think you can send voice messages as well in secret chats but im not 100% positive on that), or an encrypted texting app like
Silence. If you want encrypted voice, you'll need GAPPS in order to download
Signal, which is basically Silence with voice and uses data instead of SMS for encrypted messaging. All those are predicated on the person you want to communicate with using those apps as well.
hope that answered your question, dont be afraid of rooting and adding roms. it requires some reading up on the subject, but its not hard once you get the jist of it.