Looks nice. Pleasant, plausible shapes, and a nice mix of flat vs. steep. Apart from any scale indicators the mountains seem like individual ridges and peaks, yet at the scale you indicate one would expect a bit more branching - whole systems of mountain ranges. You have diligently sourced every river at a mountain - and right up high on its flanks at that. While some streams do rise in the mountains, plenty of others have their sources in less precipitous terrain. Too, up at its highest reaches one of those mountain rivers would be a tiny stream, and at this scale of map perhaps not worthy of notice. You've done well with keeping river locations plausible, except I'm not buying the ones that run the length of a peninsula - like that near Onash, the one near Rilvas, the one by Thrivar, and so forth. Such a circumstance is not impossible, one would just expect terrain that forced it - say, twin ridges 'containing' the watercourse. Absent hints like that, I'd expect stream flow to 'fall off' to one side or the other.
I want the Engill canal franchise, by the way. :-) Or the ferry concession at Tayli.
You look like you've got a vague prevailing wind from northwest going - is that right? Is the tan terrain supposed to be arid? Across such a vast expanse I'd expect some more variation in generalized airflow - UNLESS you're playing your definition of 'giant planet' to the hilt. Care to give us a diameter? Have you thought what latitude you want Segarma to be at?
You've wondered elsewhere about forest placement - I'd say you are doing fine. I do see some extensive river systems that are exclusively in arid areas - you might want to indicate an in-between climate zone - steppe or savannah or the like?
I don't know the Saderan process - are the bits of continental shelf generated or painted, as it were? If you can easily paint some more, broader shallow expanses would do well in places.
Would the northern of the two big Istane lakes overflow to the sea?
Good stuff - keep it up. I find myself wanting to know more about your lands, which is a good sign!