Noncollinear ferrimagnets combine a net magnetic moment with internal spin degrees of freedom, creating opportunities to couple magnetic, mechanical, thermal, and electronic responses. Using first-principles calculations, symmetry analysis, atomistic spin simulations, and transport modeling, we identify stable NbMnX₂ (X = S, Se, Te) monolayers with noncollinear ferrimagnetic ground states and Curie temperatures up to 313 K. Competing exchange, Dzyaloshinskii–Moriya interactions, and magnetic anisotropy produce field-responsive canted states that couple strongly to the lattice and charge carriers. Magnetization rotation changes the elastic modulus of NbMnTe₂ by up to 36%, while lattice entropy substantially enhances the near-room-temperature magnetocaloric response of NbMnS₂ and NbMnSe₂. In NbMnSe₂, rotation restores a mirror-protected crossing, continuously closes an approximately 0.13 eV gap, and produces a conductivity-based anisotropic magnetoresistance ratio up to 10,000% at 100 K. The combined results establish noncollinear NbMnX₂ monolayers as a multifunctional platform for two-dimensional spintronics, nanomechanics, and thermal control.