LCD prints black text on blue screen, but can print white on blue when bugged out
That is a contrast pot. Not a brightness pot. And it is a white backlight, with inverse segments. So background should be dark and the pixels white.
So the pot must not be set to maximum brightness, as it means you have zero contrast and you can see it extremely poorly.
When there is something on the screen, adjust the contrast pot so that you have dark background and bright letters and good viewing angle.
Also, many displays don't work with 3.3V and require 5V. Make sure you have a 3.3V display if you are going to run it on 3.3V supply. Note that the backlight may require different voltage, that may not be 5V compatible backlight.