Here's my reference though I've heard people talk about better battery life before this reddit post
This website will explain exactly how adaptive battery works. If you want to see which apps it's controlling on your phone open developer options, scroll down near the bottom and Tap on the item titled Standby Apps. If you turn off adaptive battery all the apps listed in there will be placed in the active bucket. No restrictions.
I've turned it off for a few days and really didn't notice any battery usage improvements. I have it turned on and I have good battery usage stats most of the time. The power mode optomized is the settings I use and never change it. The optomization service does all the heavy lifting regarding battery life. Just another opinion really.
It's not going to harm your phone in any way if you turn it off for a few days. When you turn it back on it will go back to learned app usage it logged before you turned it off and continue monitoring and learning. Best to judge for yourself on your own phone I think. Let us know what the results are if you have time.
Thanks for posting the results. That's interesting. I turned it off again a few minutes ago. Two services that use battery during overnight device idle cell standby disappeared from the list. I'm going to leave it off for a few days and watch the battery usage stats.