May be a stupid thing, but that is simply a must-have for me. My HTC M7 did it, and my Note 4 does it.
I had a ZTE Axon 7 for 24 hours. It had a hardware issue that required me to take it back, but might have anyway since I couldn't set individual text tones. (Too bad!! Super phone and those speakers were awesome!)
So, can this be done on the OP3??
Yes, you can set individual text tones. In the messenger app, just go into a conversation with the contact, hit the three dot menu, go into People & options, tap Sound, and select your tone. Ringtones are set on their own in the contact settings.
It took me a bit to find where to set things, because they're in different areas, but yes, you can absolutely set individual text tones on the OP3!
I almost bought the Axon 7. Had it pre-ordered, changed my mind the night before it was going to ship and got the OP3 instead. Camera raw and developer support were the big swing votes for me. Even if I'd have preferred the speakers and 2k screen! I'm actually liking having the fingerprint scanner on the front too. Not sure I'd have enjoyed it on the back as much ... I tap it a lot while it's sitting on a table or in my car mount. Front facing is definitely a plus in those situations!