There are two meanings of QM. The first meaning of QM is the general structure as a theory of observables and Hilbert spaces etc. In this sense, RQM is only a particular type of QM. In fact, RQM has some problems which can be cured by going to relativistic quantum field theory. In this first meaning of QM, relativistic quantum field theory is also a particular type of QM.
In the second sense, QM refers to non-relativistic quantum mechanics, which I shall abbreviate NRQM. This is only accurate in non-relativistic situations, and can be derived (in the physics sense) as a valid approximation from relativistic quantum field theory. In situations where the full relativistic quantum field theory is not needed, it is more convenient to use NRQM. NRQM accurately describes most condensed matter physics and quantum chemistry. In some cases in quantum chemistry, a relativistic treatment is needed, but it is still too inconvenient to use the full relativistic quantum field theory formalism, and RQM is used in such cases.
Also, my personal bias is that even relativistic quantum field theory can be thought of as ordinary NRQM by using lattice models. The main problem with this bias is that it is still not clear if chiral interactions can be properly treated in the lattice framework.
