In addition to the assumption of a neat-liquid water electronic structure, MQC methods rely also on approximate electron-molecule pseudopotentials to describe the interaction of the excess electron with the closed-shell water molecules. While much effort has been devoted to their development, these pseudopotentials introduce large sources of uncertainty in the accuracy of MQC descriptions of e - aq . Unlike typical atomic pseudopotentials that replace core electrons, the electron-molecule a) Electronic mail: william.glover@nyu.edu pseudopotentials replace valence electrons, which introduces an uncontrolled error. Furthermore, the structural predictions of MQC simulations of e - aq can depend quite sensitively on the pseudopotential, which one of us found recently to arise from a competition of entropic and enthalpic driving forces in the solvation structure of e - aq . A first-principles description of e - aq is thus preferred, and several ab initio molecular dynamics (AIMD) strategies have emerged recently, including Quantum Mechanics/Molecular Mechanics (QM/MM), periodic planewave Density Functional Theory (DFT), periodic second-order Möller-Plesset theory (MP2), and Path Integral Molecular Dynamics (PIMD) with Machine-Learned (ML) potentials. Given the computational cost of ab initio methods, explorations of the equilibrium dynamics of e - aq have so far been limited, although the initial localization dynamics has received attention. An exception is the very recent PIMD study of e - aq with ML potentials, which afforded extensive sampling due to the forcefield-like cost of ML potentials. Of the AIMD methods, QM/MM is particularly efficient, since most of the solvent molecules far from the electron can be treated with a cheap MM forcefield, and only the first few solvent shells around e - aq need to be treated at a QM level. However, a problem arises since water is diffusible, and without a special treatment, the QM and MM water molecules would mix, leading to a breakdown of QM/MM separation. This limits the length of trajectory that can be simulated to a few ps. The issue of QM/MM mixing by diffusible particles is precisely addressed by our Flexible Boundary Layer using Exchange (FlexiBLE) method, introduced in the previous companion paper. FlexiBLE belongs to a class of constrained QM/MM methods that maintain QM/MM separation by applying a repulsive potential on particles near the QM/MM boundary. We showed in paper I that with a careful choice of boundary potential, QM/MM separation can be maintained while leaving en-semble averages unaffected and allowing for density fluctuations in the QM region. Unlike adaptive QM/MM approaches, FlexiBLE prevents QM or MM particles from traversing the boundary, meaning long-time diffusional dynamics will not be accurately described. However, we showed in paper I that FlexiBLE preserves equilibrium dynamics in the inner QM region, at least on sub-diffusional timescales, which is sufficient to simulate e - (aq) 's vibrational spectroscopy. To explore the influence of an excess electron on water's electronic structure and dynamics, we performed many-electron FlexiBLE-QM/MM AIMD simulations at the BH&HLYP-D3/6-31++G* level on a model of the condensed-phase e - (aq) . We find that the equilibrium dynamics of the electron exhibits enhanced coupling to OH stretch modes compared to an MQC description. By performing Natural Bond Orbital (NBO) analysis, we show that this coupling arises from significant occupation of OH σ * antibonding orbitals, in a similar fashion to that observed in water anion clusters. This allows us to develop a minimal frontier orbital description of e - (aq) involving a cavity orbital and strong coupling to 4-5 OH σ * orbitals. e - (aq) can thus be viewed as a strong hydrogen bond acceptor.