In this paper we study regularity and topological properties of volume constrained minimizers of quasi-perimeters in RCD spaces where the reference measure is the Hausdorff measure. A quasi-perimeter is a functional given by the sum of the usual perimeter and of a suitable continuous term. In particular, isoperimetric sets are a particular case of our study.We prove that on an RCD(K, N ) space (X, d, H N ), with K ∈ R, N ≥ 2, and a uniform bound from below on the volume of unit balls, volume constrained minimizers of quasi-perimeters are open bounded sets with (N − 1)-Ahlfors regular topological boundary coinciding with the essential boundary.The proof is based on a new Deformation Lemma for sets of finite perimeter in RCD(K, N ) spaces (X, d, m) and on the study of interior and exterior points of volume constrained minimizers of quasi-perimeters.The theory applies to volume constrained minimizers in smooth Riemannian manifolds, possibly with boundary, providing a general regularity result for such minimizers in the smooth setting.