Re: IOS 10 messages background activity
I started using the beta a few weeks ago. Sorry, I never saw this on my 6s. I just looked - no background activity in Messages in the last 24 hours. (I spent a lot more time messaging in the last 18 hours than I usually do, and right now Messages is top of my list at 15%, 36 minutes on screen, in the last 24 hours, but no background activity. When I looked yesterday it was at 1% and just a few minutes on screen. In the last 7 days, it's 3% of my battery, 1.2 hours on screen, 2 minutes background.)
I have never used (nor do I wish to use) any of the new features - stickers, balloon effects, etc. I'm with you in that I'd like to toggle it off. You can turn on Reduce Motion in accessibility settings I think to keep from seeing that stuff when it's sent to you. I just checked - I actually had that setting on all this time. Maybe that's why it's been better?
I wish I could give an answer beyond that ...