Welcome! You have a good eye for jittering a convincing variety of coastlines into place. I look forward to seeing what you come up with.

As far as leaning mountains I'm imagining an outlandish rationale... Maybe your world had ReALLY strong prevailing winds in the past :-). They look nice - props for drawing them all... Doing six to ten and using as brushes is easier but runs the rush of looking repetitive. I'll echo the recommendation for the How To Get Your Rivers in the Right Place tutorial - your plausibility will take a good jump when you get water flowing downhill realistically.

Are you pleased with MyPaint? There are really capable apps available for free or cheap that are hugely capable, and which could simplify your further progress with this.