it's a nice texting app. You can customize it in almost every possible way. Good support for emoticons, gif and other apps (drivemode, android wear, gboard...). You can assign a specific tone for each contact.
Though, i reverted to stock messaging app because textra failed to send mms for me (my provider set a 600kb limit on mms and textra doesn't compress videos when yo add them : both stock messaging and android messages can so...). Even though I contacted support about this, they replied back to tell me that level 2 support should recontact me and as of today they never did.
Note : my S7 is still on Marshmallow...