No problems for me either,
if adaptive brightness is off in settings it doesn't rely on the sensor, so the brightness level is staying constant and shouldn't flicker.
It kinda sound as if something is bad with your installation.
You mention that you had issues formatting ?
Are you sure that it effectively formatted data and that you don't have left overs from a previous rom ?
That could definitely bring that kind of issues if settings are mixed up.
Also make sure that if / when you restore things that you never restore system apps / settings.
Overall if I were you I'd try to reinstall.
format /data
flash the rom + supersu + gapps in one shot
wipe cache
reboot.
In the setup process do not choose to restore apps and see if that helps.
That way you have a full clean setup.
As for lagging, I have no lags on 031 here with a fresh install and my main apps restored.
(performance on 030b were not as good, so it also depends which version you installed)
But after a fresh install it takes a bit of time to settle, it also depends what you restore and if you have lots of medias in your storage.
As apps are going to update and mediascanner is going to scan everything all around.
One of the first thing I do myself is set a mediascanner "white list" filter to /system/media and reboot
that way it doesn't scan everything all the time

and I simply use a filemanager to open media I want