Chromium in its initial configuration also feels like a gnome from Mars.
First, make sure that the Chromium installation did not change the default browser:
KDE System Settings > Apps & Windows > Default Applications > Default Applications > Web browser: Firefox
Then, there is a major problem: There is no way to raise/lower the Chromium window.
It's not a problem with the KDE setting. It's a problem caused by Chromium.
The fix:
Settings > Appearance > Use system titlebars and borders: Enable
Other customizations:
Settings > Languages > Spell check > Check for spelling errors: Disable
There's no way to make this browser ad-free. Google prevents that.
