Is the content searchable like HubSpot Academy

Yes, to an extent.

Out of the box you can use HubSpot's Search features (and search template included in HubLMS) to make searching all your pages. Any content that is shown default on the page is available to search. This includes the overview page, but NOT the lesson detail content.

If you have keyword-rich lesson titles they would be indexed along with the overview text on your page.