I run a dark theme by default, first load of google.com in chrome is functionally indentical in performance as I said. Statistically there is a difference, probably only 0.1 - 0.25s max faster load in Chrome but it’s not reliable at all in the few tests I did quick (t’s 4am), so something that does not effect function itself, only form, makes me still correct in what I said originally.
That’s just my werid phrasing, I mean the non-chromium branch that is Firefox and its backend.