Subwavelength confinement enabled by bound states in the continuum (BICs) provides an effective pathway to enhance light–matter interactions in compact photonic systems. In particular, radial quasi-BICs offer polarization-invariant, high-Q resonances within an ultrasmall footprint, holding great potential for on-chip applications. However, conventional realizations relying on geometric asymmetry face fabrication challenges due to the difficulty of precisely controlling nanoscale structural perturbations. Here, we propose a compact and scalable nanophotonic platform that supports radial quasi-BICs via intrinsic and environmental permittivity asymmetry without geometric modifications. By systematically comparing geometric and permittivity asymmetries, we demonstrate their equivalent optical responses both exhibiting inverse-square scaling of the radiative Q factor. Based on intrinsic material modulation using silicon-rich nitride, we engineer quasi-BICs near 1565 nm with Q-factors exceeding 9000. Building upon this insight, we realize environmental permittivity asymmetry by embedding rod-pair resonators in different environment, enabling dynamically reconfigurable high-Q resonances. The devices achieve average Q factors over 3000 and sensing figures of merit exceeding 366 RIU^-1 in an ultracompact footprint, with vertical emission compatible with all-fiber integration. This work highlights the potential of permittivity asymmetry as a robust and lithography-tolerant design strategy for next-generation high-performance photonic devices.