The generation and manipulation of nonclassical light are of fundamental importance in quantum optics and quantum information processing. Although various mechanisms have been proposed for realizing photon blockade and multiphoton emission, achieving programmable control over distinct photonstatistical behaviors within a single cavity quantum electrodynamics (QED) platform remains challenging. In this work, we investigate a cavity-QED system consisting of a four-level atom coupled to a single-mode cavity and propose a drive-selective mechanism for programmable control of photon statistics. Operating in the large-detuning regime, the intermediate state is adiabatically eliminated, yielding an effective model that simultaneously contains a two-photon Jaynes-Cummings (JC) nonlinear interaction and a cascade-assisted coupling channel. By solving the quantum master equation and analyzing high-order correlation functions, photon-number distributions, and time-dependent correlations, we systematically study the nonclassical emission properties under different driving conditions. We find that the cavity driving and atomic driving activate different excitation manifolds and therefore lead to distinct quantum statistical behaviors. Under cavity driving, the system predominantly populates the single-excitation manifold and exhibits strong photon blockade with pronounced antibunching, resulting in high-purity single-photon emission. In contrast, atomic driving preferentially excites the two-excitation manifold, where the cooperation between the two-photon JC nonlinearity and the cascade coupling channel opens an efficient two-photon transition pathway. Consequently, the system generates stable two-photon bundle emission characterized by enhanced second-order correlations, suppressed higher-order correlations, and antibunching between successive photon bundles. To reveal the underlying physical mechanism, we further analyze the excitation spectrum. The single-photon emission originates from resonant transitions in the one-excitation manifold, whereas the two-photon bundle emission is associated with resonant processes in the two-excitation manifold. In particular, when the states |2, g〉 and |0, m〉 become nearly degenerate, the direct two-photon transition is strongly enhanced, while the intermediate state contributes through virtual processes and modifies the resonance condition. The interplay between direct two-photon conversion and cascade-assisted excitation provides an effective excitation-pathway selection mechanism. When both driving fields are simultaneously applied, the system supports the coexistence of single-photon and two-photon emission channels. By tuning the detuning and coupling parameters, a continuous transition between these two nonclassical emission regimes can be achieved. Our results demonstrate that photon statistics are governed not only by nonlinear interactions but also by the cooperative interplay among driving configurations, excitation pathways, and spectral structures. This work establishes a general framework for programmable quantum-light generation and provides a feasible route toward multifunctional quantum light sources in cavity-QED and related quantum photonic platforms.