Dark theme works well with the Dracula color scheme.
Note, using this in Mate gives a little bit of an error which can be fixed by running the following command in the metacity-1 subdirectory of the theme:
ln -s metacity-theme-3.xml metacity-theme-1.xml
Thanks for the update!
I noticed that Gnome Web looks a bit off with biggish font sizes (e.g. my usual 13pt Source Sans Pro here). The headerbar is too compact for it really. It seems most pronounced when Web uses a header bar with a subtitle, for example when it's running the the little apps you can create with its "Install Site as Web Application..." from the 3-dots menu. Here, the subtitle gets cut off halfway through the line. The problem also make the address bar for Web's normal mode bump into the base of its container, and it doesn;t look correct to me.