The Note 5 must have a different setting than the S6 and S7. I have an S6 and the widget definitely forces it into the highest brightness mode, which is what the widget is intended to do. It should be so bright that you can hardly look at it indoors.It gets a little brighter, not as crazy bright or whatever happens when outdoor mode kicks in but it gets brighter indoors.
***after testing on my note 5 with lux meter from the playstore (on my note 3). I have some results that are slightly more useful than just my eyeball tests***
HBM off
420 on full brightness indoors
590 on full brightness when outdoor mode starts
HBM on
450 on full brightness indoors
590 on full brightness when outdoor mode starts
But when outdoor mode turns off after a few seconds it goes back to 420 and you have to toggle HBM to get it back to 450
Samsung has some weird settings they implement that seem to be affecting our screens performance.
http://forum.xda-developers.com/showthread.php?p=62643611
They also have a weird way of having autobrightness work differently when you are holding it compared to when it is laying flat on a table. So they have pretty much F'd with the way google intended everything as usual.
When I have some more time, I will release a beta version to try out some different settings.