  We consider an interacting collective spin model known as coupled top (CT),
exhibiting a rich variety of phenomena related to quantum transitions,
ergodicity, and formation of quantum scars, discussed in [Phys. Rev. E 102,
020101(R) (2020)]. In this work, we present a detailed analysis of the
different type of transitions in CT model, and find their connection with the
underlying collective spin dynamics. Apart from the quantum scarring phenomena,
we also identify another source of deviation from ergodicity due to the
presence of non-ergodic multifractal states. The degree of ergodicity of the
eigenstates across the energy band is quantified from the relative entanglement
entropy as well as multifractal dimensions, which can be probed from
non-equilibrium dynamics. Finally, we discuss the detection of non-ergodic
behavior and different types of quantum scars using `out-of-time-order
correlators', which has relevance in the recent experiments.
