α and cluster decays are analyzed for heavy nuclei located above 208Pb on the chart of nuclides: 216–220Rn and 220–224Ra, which are also candidates for observing the 2α decay mode. A microscopic theoretical approach based on relativistic energy density functionals (EDF), is used to compute axially symmetric deformation-energy surfaces as functions of quadrupole, octupole, and hexadecupole collective coordinates. Dynamical least-action paths for specific decay modes are calculated on the corresponding potential-energy surfaces. The effective collective inertia is determined using the perturbative cranking approximation, and zero-point and rotational energy corrections are included in the model. The predicted half- lives for α decay are within one order of magnitude of the experimental values. In the case of single-α emission, the nuclei considered in the present study exhibit least-action paths that differ significantly up to the scission point. The differences in α-decay lifetimes are not only driven by Q values, but also by variances of the least-action paths prior to scission. In contrast, the 2α decay mode presents very similar paths from equilibrium to scission, and the differences in lifetimes are mainly driven by the corresponding Q values. The predicted 14C cluster decay half-lives are within three orders of magnitudes of the empirical values, and point to a much more complex pattern compared with the α-decay mode.