I wouldn't suggest to add a built-in VPN and a built-in AdBlocker as not all users need them, that's why they are optional, to download as extension. I'd recommend AdBlocker Ultimate, I found it cool and really simple to customize (and blocks trackers, an addition to your Advanced anti-tracking protection setting). If you already set the dark theme but would like to set webpages, too, you can change text colour to white and page background to black. For improved protection enable Restrictive on Advanced anti-tracking protection settings section and disable it temporarily from the shield icon on the address bar if you think that the page isn't working (can happen sometimes blocking certain contents with this security option).
