We explore anomalous skin effects at non-Hermitian impurities by studying their interplay with potential disorder and by exactly solving a minimal lattice model. A striking feature of the solvable single-impurity model is that the presence of anisotropic hopping terms can induce a scale-free accumulation of all eigenstates opposite to the bulk hopping direction, although the nonmonotonic behavior is fine tuned and further increasing such hopping weakens and eventually reverses the effect. The interplay with bulk potential disorder, however, qualitatively enriches this phenomenology leading to a robust nonmonotonic localization behavior as directional hopping strengths are tuned. Nonmonotonicity persists even in the limit of an entirely Hermitian bulk with a single non-Hermitian impurity.

The remarkable sensitivity of non-Hermitian systems has been extensively studied and stimulated ideas about developing new types of sensors. In this paper, we examine a chain of parametrically driven coupled resonators governed by the squeezed Su-Schrieffer-Heeger model. We emphasize the qualitative difference in sensor performance between configurations depending on bulk topology and boundary modes, specifically for detecting both on-site and non-Hermitian skin effect perturbations. Our analysis goes beyond the scenario of infinitesimal perturbations, extending to arbitrary perturbation strengths beyond the linear response regime. We stress the importance of optimizing the system's parameters to achieve quantum enhancement while avoiding fine-tuned regimes that could limit the practical applicability of this system for real-world quantum sensing.