Fairly new to blender nodes. How can I keep the alpha part of a 2d image texture, without having a principled BDSF changing the lighting/brightness of the original image? This is what I want, but without the brightness effects
You want to connect it like this:
You can connect your image as an (unshaded) input into a mix shader, with a Transparent BSDF in the other slot. Use the image's alpha output as a mix factor.
Also, for best color accuracy, make sure your view transform is set to "standard" (instead of default "filmic").