Installed 16.3 core this week and have been setting it up and tinkering with settings> My Q how do I adjust the screen contrast and brightness as it is too bright?
thanks
You can adjust brightness both on Settings > Energy or holding fn + the keys that you see with a small sun 
and a big sun 
. For contrast you have to install a software. By default you can enable High Contrast on Accessibility but makes contrast really high, you don't customize it.
If you are using the Cinnamon DE there is an app you can install that lets you adjust everything like brightness, color balance and gamma. Here is a link to my thread I posted earlier today about Qredshift.