This paper presents a comprehensive study of highly excited Rydberg states in 174Yb and 171Yb atoms, focusing on their spectroscopy and modeling using multichannel quantum defect (MQDT) theory. The authors develop refined MQDT models for the Rydberg states of 174Yb with \(L \leq 2\) and extend these models to describe the Rydberg states of 171Yb with \(L \leq 2\), incorporating hyperfine interactions. The models are validated through detailed comparisons with experimental measurements of Stark shifts, magnetic moments, and Rydberg interactions. Using these models, the authors compute interaction potentials between pairs of Yb atoms and verify them against direct measurements in an optical tweezer array. They identify an anomalous Förster resonance in the previously used \(F = 3/2\) Rydberg state, which likely degraded the fidelity of entangling gates. By identifying a more suitable \(F = 1/2\) state, they achieve a state-of-the-art controlled-Z gate fidelity of \(F = 0.994(1)\), with the remaining error fully explained by known sources. This work establishes a solid foundation for future quantum computing, simulation, and metrology applications using Yb neutral atom arrays.This paper presents a comprehensive study of highly excited Rydberg states in 174Yb and 171Yb atoms, focusing on their spectroscopy and modeling using multichannel quantum defect (MQDT) theory. The authors develop refined MQDT models for the Rydberg states of 174Yb with \(L \leq 2\) and extend these models to describe the Rydberg states of 171Yb with \(L \leq 2\), incorporating hyperfine interactions. The models are validated through detailed comparisons with experimental measurements of Stark shifts, magnetic moments, and Rydberg interactions. Using these models, the authors compute interaction potentials between pairs of Yb atoms and verify them against direct measurements in an optical tweezer array. They identify an anomalous Förster resonance in the previously used \(F = 3/2\) Rydberg state, which likely degraded the fidelity of entangling gates. By identifying a more suitable \(F = 1/2\) state, they achieve a state-of-the-art controlled-Z gate fidelity of \(F = 0.994(1)\), with the remaining error fully explained by known sources. This work establishes a solid foundation for future quantum computing, simulation, and metrology applications using Yb neutral atom arrays.