High-quality proton beams generated by laser-plasma interactions are of significant interest for applications ranging from tumor therapy to fast ignition in inertial confinement fusion. However, simultaneously achieving high energy coupling efficiency and beam collimation remains a challenge. In this work, we investigate the enhancement of proton acceleration via geometric confinement in near-critical density (NCD) plasma-filled micro-structured targets using two-dimensional particle-in-cell simulations. To optimize laser-to-particle energy transfer, we systematically compared various target configurations, such as rectangular tubes, hybrid funnels, and straight cones. Our results reveal that the acceleration performance is not governed simply by the overall geometric complexity of the target. Among the tested geometries, the straight-cone and projectile-shaped targets form the leading-performance group, both producing higher cutoff energies and high-energy conversion efficiencies than the rectangular and funnel-shaped targets. Their common advantage is the presence of cone-like confinement near the rear foil, which promotes hot-electron focusing and helps sustain the rear-side sheath field. The straight-cone target shows a modest advantage in cutoff energy and beam-core collimation under the present parameters, reaching a maximum proton cutoff energy of 181.7 MeV and a divergence of approximately at a laser intensity of W cm. This enhancement is attributed to the synergistic effect of relativistic laser self-focusing within the NCD plasma-filled channel and the spatial confinement of hot electrons by the cone-like geometry. Furthermore, we identify a double-peak structure in the temporal evolution of the electron energy, which supports the interpretation of sustained electron refluxing. This refluxing mechanism helps maintain a robust sheath field over an extended duration, contributing to the enhanced acceleration in the leading cone-like geometries. The proposed target concept may provide a useful design principle for generating high-flux, high-energy proton beams suitable for next-generation high-repetition-rate laser facilities.