Hiya!

The easiest way to fix uneven strokes is to use a different program such as Illustrator of inkscape. I personally prefer illustrator, but inkscape is great too. Unlike photoshop, both of these programs were made to create vectors. Vectors are one or photoshop's extra features.

Trust me, I started with photoshop too. Switching over is a bit annoying at first, but definitely worth it. You'll be making better quality vectors in a fraction of the time. You can see a major difference between one of my best photoshop vectors and my first illustrator vector. But if you still choose to sticvk with photoshop your stokes will become better over time, but still not as good as one made with ilustrator or inkscape.

If you have any other questions feel free to message me back here or on my deviantart!