Relational Quantum Mechanics (RQM) defines physical states relationally but does not specify how relational structure itself becomes articulated. The Relational Emergence Model (REM) introduces a generative layer beneath relational description, modeling relational articulation as a variational selection problem over Hilbert-space factorizations: Φ = Φ_S + λ Φ_H combining informational differentiation and dynamical stability. The parameter λ acts as a control parameter governing the balance between informational structure and dynamical coherence. A three-qubit example with H = Z₁Z₃ demonstrates genuine regime competition: at λ* ≈ 0.3672 the selected factorization switches from the informationally optimal A|BC partition to the dynamically stable B|AC partition (zero boundary coupling). Physical interpretation of λ via decoherence timescales and a minimal open-system model are provided. Relation to REM5 (quadratic cost) and Carroll–Singh quantum mereology are discussed. This paper is part of the Relational Emergence Model (REM) series (REM_lambda).