Gene regulatory networks should be definitely studied as a cell-type specific events. So its better to study them at single cell level or from highly purified cell-types with bulk RNA-Seq.

SingleCell RNA-Seq is still sparse to study global gene regulatory networks. At most, you could get cell-type specificity of genes. The regulatory networks inferred from scRNA-Seq data are not robust and may give hints but not conclusive as there is lot of expression variability due to technical and biological reasons.

There is a nice review Co-expression in Single-Cell Analysis: Saving Grace or Original Sin? about co-expression in scRNA data which might be useful for you.

There is a paper Renal compartment–specific genetic variation analyses identify new pathways in chronic kidney disease I read recently where the authors performed bulk RNA in different Kidney compartments and got better insights into GWAS of CKD instead of studying the whole tissue. This definitely supports GRN as cell-type specific events.