Hi there,
Using a page builder tends to slow your site down a bit for sure.
However, it also depends on what modules you are using from the page builder and how much you are using it.
I’ve seen examples where the site loads quite fast with the usage of page builders as well.
We are working on a block plugin (not quite a page builder) and the beta should be released relatively soon now. It’s in the final stage of testing and tweaking as we want to get it right.
Thanks for your patience 🙂