You are off to a great start. With some more work and practice you will have great maps to show off.

For the "drawn elements"... it looks like you are re-sizing them. A better way is to draw them bigger or smaller, rather than re-sizing them. (I have been guilty of that too). The best way to make things match is for them to really match :-)

For drawing with the mouse. I recommend zooming in and using a mix of "click/drag/undo" and the "many little shift clicks" (moving the mouse only a short amount and shift clicking). Because you don't get pen pressure with a mouse, changing the brush size helps as well. If your outside lines are 8 wide then add the detail lines with a 6 and 4 to give you the feel that those lines are not as "hard". With practice you can get good curved lines with the "many little shift clicks" (but it is hard with a mouse to really get amazing results).

Even if you only make a one or two mountains in just three different sizes you can get really nice looking results (3-6 Mountains and maybe 2-4 hills is a great start)... Make the elements next to each other in a new file with each element on a new layer, then drag them into your main map as many times as you need them. Something else that helps is removing/erasing the parts of lines that overlap after you move the elements together based on what is on "top".

Keep up the good work and you will have a great map before you know it!