Maybe Hashnode can take a hint from this poll. I simply install an invert colors application on my system. It works well for reading online.

Using auto indentation, I hardly find myself pushing tabs or spaces. But internally, I set my IDE to expand tabs to spaces. You have to work across platforms to realize how messy tabs can get.

If you are looking for a light-weight option, may I suggest Lubuntu or LXLE. Both are super light on resources. I have tried LXLE on my 2010 macbook air. Works pretty well. My main reason for choosing LXLE was its low memory footprint. My laptop has 2GB RAM and with any modern browser, it gets slow very quickly.