how good are we at plunging shots?
With stationary targets, if it can be physically done with a bow and arrow, Ivara can do it. It is after all, simple geometry. (Ivara is also very good at the more practical aspects of maths.) She'd really only struggle to shoot at fast moving targets (at least, fast moving for a Tenno,) or stationary targets around a kilometre or so away, but even that's not really a problem if she can find a spot to use Navigator to correct the arrow's course without being interrupted. At some point though, even Ivara has to admit that using a rifle is simpler and like all Tenno, she is proficient with many, many weapons. But she does love her bows, so if she can avoid taking rifles, she'd do it as a matter of personal preference.
It is really just a matter of equipment limiting her right now. There's only so much you can do with wood, plastic and light metals. Remember, the Paris/Paris Prime used magnetic Orokin-tech bullshit to launch incredibly dense heavy-metal kinetic penetrators. The other bows are using generally rare, high performance alloys and materials to leverage the pretty hilariously broken strength of most warframes, and some of them fire some pretty wacky arrows that have some pretty weird aerodynamic properties.
Fun thing to consider: you can hold a draw on all bows pretty much indefinitely,
except for the Daikyu. Think about it. Would holding the draw for too long break the Daikyu? Or does it have such a heavy draw that even warframes can't hold it for too long?
Ivara's Artemis bow is the real kicker of the lot, however. Being able to fire 'arrows' made of pure Void energy is pretty bullshit and requires some fairly impressive (and pretty bullshit) feats of engineering; consider the number of Nitain Extracts and Argon Crystals you need to build an Ivara...
Depending on how much energy she puts into it, the 'arrow' will fly straight and true (or around in circles, whatever she wants it to do, really,) until it loses coherence, which can be quite a while. And because it uses Void energy instead of a physical projectile, it is as lethal at 100m as it is at 3000m, and can punch through some pretty thick armour and several layers of energy shielding while doing so.
The Orokin were pretty big on Voidhax.