Jet substructure techniques for new physics searches have become mainstream in the last decade, however precise theoretical calculations and experimental measurements of substructure observables have been sparse. We will talk about the most extensive such measurement made by ATLAS, and what we learn from comparison of different model predictions. We will present a study on how detector smearing changes the shape of these observables, and how that is not currently accounted for in the smearing tools like Delphes. As we have not seen any signatures of new physics so far, it is imperative that we look at unusual and experimentally challenging topologies. The boosted heavy neutrino search in ATLAS looked at a large-radius jet containing an electron as a physics object for the first time, which will be discussed.