I'm going to try to make this as simplified as possible.
To truly answer your question, proper exposure is the histogram rounding up at the middle maybe edging closer to the highlights where all image detail is clear,highlight and shadow is neither blown out or underexposed and have flexibility to be adjusted. In Lightroom you can check with J. This is the text book answer.
Here are my opinion and answers. Truthfully, you need to understand your image composition and style.
I veer more towards the bright and airy style, so I'll want to under expose my images when photographing on digital to retain the highlight and brighten up all the shadow details in post processing.
If you're able to identify how you photograph, understanding the exposure techniques to photograph what best suits your need when editing will help you tremendously.
Hope I was able to help!