A microscopic theory of the structure of compressible associating AB regular heteropolymer fluids is proposed based on polymer integral equation methods. The theory is employed to systematically explore, as a function of temperature, the influence of sticky group attractive energy, concentration, degree of blockiness, and global architecture (telechelic, surfactant, multiblock) on self-assembly and microdomain formation as encoded in small-angle partial scattering structure factors. Characteristic apparent spinodal and order-disorder temperatures are estimated, and strong composition fluctuation effects are always present. The evolution of collective properties derived from scattering profiles such as microdomain period, intermultiplet coherence length, degree of Porodlike scattering, and modification of wide-angle intensity, with polymer structure and thermodynamic state are established. At fixed bare (chemical) driving force, end-functionalized architectures are found to form more ordered microphase-separated fluids than the multiblock analogues. Increasing sequence length also enhances self-assembly even at fixed global sticky group composition. Significant differences between telechelics composed of unimer sticky groups vs mini-triblocks are found, with the former displaying many self-assembly features not in accord with classic block copolymer behavior. Semiquantitative comparisons with small-angle X-ray scattering experiments suggest the theory provides a realistic description of self-assembly in ionomer melts, and failure of incompressible random phase approximation approaches for many properties is documented. Predictions for the majority (nonpolar) monomer density fluctuations, and cross-correlations, are obtained. Subtle, but systematic structural changes are induced by the minority group self-assembly process which may be amenable to direct measurement using small-angle neutron scattering and are possibly of mechanical property relevance.