What exactly is serp features?

Anything on the results page that isn't a plain blue link. Featured snippets, People Also Ask boxes, the local map pack, image and video carousels, shopping results, AI overviews, that sort of thing. For a 40 page site I wouldn't chase them as a project. Write pages that answer the question clearly near the top and use proper headings, and you'll pick up the odd snippet or PAA spot as a side effect. The exception is local: if you serve an area, the map pack is the one worth real effort.