Thank you for the nice compliment, Azelor.
I have a tablet, but I find it's just as easy to use a mouse for anything that doesn't need pressure control. I use a thumbball mouse and I have better control with it than with the tablet pen, mostly because my hand rests stationary on the mouse. With the pen, my hand is less stationary, and thus I get more unwanted jitter.
If you look closely at the rivers here, I used the pen to make the tapering ends of the rivers, although even there, PS fade with the mouse works about as well.