Specifically, which Blogs/Books/Speakers/Experts have the leading ideas and most helpful material on how to improve the scalability of a company. This question is not limited to startups, but any growth oriented company. Let's assume the company has achieved product/market fit ... now what? What are the leading ideas or principles for scaling, and who has them?
Nichole's list is comprised of people who talk about growth marketing. Although growth marketing is a component of scaling-up, scaling a company is much more about operational issues. Everything from tech stack to culture to legal and compliance and almost always sales.
On growth, there are a lot of people who talk about the principles of growth from a marketing perspective and a couple of people on Nichole's list are known for *talking* about growth but I'm generally wary of people who are more known for *talking* than actual notable accomplishments in growing products.
Ivan Kirigin (formerly on Dropbox's growth team, now running a company I invested in called YesGraph), Gustaf Alstromer (AirBnb growth team), Elliot Shmukler (helped LinkedIn grow from 20m to 200m members, now in-charge of growth at Wealthfront who has been absolutely killing it), Drew Dillon (an early PM at Yammer, now Head of Product at AnyPerks), are all active on Twitter. Actually Elliot isn't but you can still search quotes he's made about growth via Twitter using his name.
If you have more specific questions, am happy to try and point you to the right resources.