This thesis plunges into the enigmatic formation of the hot Neptune desert, a sparsely populated region of exoplanetary demographics, by exploring the processes that shape close-in exoplanets. Central to this inquiry is the interplay between atmospheric evaporation and orbital migration, two pivotal mechanisms governing the evolution of planetary systems. While atmospheric erosion can strip hot Neptunes into smaller cores, the migration paths of planets near their stars determine their exposure to such irradiation. Observational measurements of spin–orbit misalignments, which differ significantly based on migration history, provide key insights into these phenomena. Through both theoretical investigations and observational analyses, this research contributes to the larger understanding of how these dynamic interactions sculpt the diversity of exoplanet populations.

This work fits the scope of such endeavor through extensive observational campaigns, in particular under the lens of the Rossiter–McLaughlin effect, which opens a privileged window allowing us to quantify spin–orbit alignment. The observational efforts, further embedded within robust statistical analyses, culminate in the Desert-Rim Exoplanets Atmosphere and Migration (DREAM) project. By assembling a comprehensive dataset of spin–orbit angles, this project offers new evidence connecting tidal forces to alignment in planetary systems, advancing our understanding of tidal dissipation across different stellar and planetary configurations. The results not only refine our assessment of planetary evolution, but also offer predictive power for future discoveries, especially in foreseeing orbital architectures at the ensemble level.

At the heart of this study lies the development and application of the JADE code, an extensive tool that integrates orbital and atmospheric evolution to better understand late-stage migration scenarios. By synthesizing the intricate feedback loops between atmospheric mass loss, secular and disruptive orbital changes, and tidal interactions, JADE provides a nuanced view of the forces shaping hot and warm Neptunes. The case of GJ 436 b, a Neptune-size planet on an eccentric, polar orbit within the desert, exemplifies the complex histories that such planets can undergo. Here, JADE reveals how resonance-driven late migration may explain the planet's unusual characteristics and endurance to intense stellar irradiation, highlighting a profound link between its orbital dynamics and atmospheric evolution. The hidden companion responsible for all the turmoil in the dynamical past of GJ 436 b is further constrained by current-day observations, thanks to a novel semi-Bayesian framework. The versatility of JADE and its future deployment on a larger scale promise to illuminate the broader physical mechanisms underpinning planetary migration, thus sharpening our grasp of the desert's boundaries and the rich evolutionary histories concealed within.