I’ve not experienced the voice feedback as it’s not supported on the 5 peak. However, for many years I’ve used iSmoothRun and it has really good control over the voice feedback.
With iSmoothRun you can:
specify how often you get general status updates - by time or distance - and whether you want them on auto lap or after intervals
control exactly which metrics (from a list almost as long as Suunto offers for display config), in which order, you are told
control whether to just hear the metrics or also the units
control the speed of the voice
pick whether to receive zone alerts for pace, hr and power (e.g. “Zone 2”)
choose to have out-of-target-range alerts (e.g. “above zone”) based on structured workouts or basic zones
receive updates on target range occasionally to confirm you are still in range
have your next step in a structured workout read out a few seconds before it starts (“30s at 3:45 … go”)
receive end of interval/session distance countdowns (800m, 400m, 200m, 100m)
setup alerts for hydration and nutrition every x minutes
Honestly, if you wanted, you’d rarely need to look at the display when using iSmoothRun and I’d love to see similar capabilities from Suunto. As you say, it’s an app thing so hopefully easier to implement than if it was on the watch.
As a side-note, iSmoothRun and other apps have similar “ducking” problems with some music sources where the volume of the original audio doesn’t return to normal. I get the impression it’s an issue with Apple’s audio framework and how different apps have implemented audio control. Spotify commonly seems to have issues, for instance.