Yeah, I’d say Opal>Menja>Mt Lady>Ginormica. Opal has extra powers and limbs as well as experience, Menja is experienced, can shift her size and has extra protection from her power, Mt Lady can size shift and has training as a hero. Ginormica is clearly at a disadvantage here, she has less options tactically since she’s stuck in giant form and she’s basically a civilian with barely any combat experience.
Yeah, this sounds about right.
It’s also worth noting that Menja’s size shifting is more versatile than Mt. Lady’s, since according to the MHA wiki, Mt. Lady only has two sizes she can be: 1.62 m or 20.62 m. Menja can adjust her size gradually, which might come in handy. On the other hand, maybe this means Mt. Lady’s growth/shrinking is much faster, which could be used to hide and then suddenly grow to catch the enemy off-guard.