Atrial Fibrillation (AF) significantly increases the thromboembolic risk, with the morphology of the left atrial appendage (LAA) being a key determinant in this process. While LAA morphological classification has traditionally relied on subjective criteria, recent studies emphasize the use of quantitative parameters (volume, depth, ostium area) to enable more objective risk assessment. This study investigated how LAA and left atrial (LA) morphology affect hemodynamics and thromboembolic risk in AF patients by performing 3D hemodynamics simulations by Computational Fluid Dynamics (CFD) in five patient-specific LA models with distinct morphological features. Enlarged atria and deeper LAA exhibited higher thrombotic risk due to low Time-Averaged Wall Shear Stress and elevated Oscillatory Shear Index and Relative Residence Time. Additionally, variations in pulmonary vein orientation and cross-sectional area were found to influence the global flow dynamics, contributing to regional differences in hemodynamic stress. Asymmetric LAA morphologies caused greater flow disturbance, while simpler shapes showed lower thrombogenic potential. The results highlight the importance of personalized hemodynamic analysis to guide interventions and stratify high-risk patients, improving clinical outcomes. 3D hemodynamic models, aligned with the digital twin concept, emerge as innovative tools in precision cardiology, integrating anatomy and hemodynamics to predict AF-related complications. This approach enables realistic simulations and supports more informed clinical decision-making.