I don't know. Both the Quarto web site and the Quarto-generated sites I have looked at seem to be rather fat.
Let's look at Lighthouse (I know it's not the be-all and end-all) for https://quarto.org/docs/websites/website-blog.html: performance score 68 with a FCP time of 2.7 seconds, and earlier today it was 4.something.
I think the gallery might be a better comparison point for what you're looking for as it shows the actual output of Quatro. E.g. https://quarto-dev.github.io/quarto-gallery/articles/html/ht... which matches your description of heading-paragraph-image type of page yields performance 99 and FCP 0.8s.
Let's look at Lighthouse (I know it's not the be-all and end-all) for https://quarto.org/docs/websites/website-blog.html: performance score 68 with a FCP time of 2.7 seconds, and earlier today it was 4.something.
That seems to be a lot.